One possible plot could be that while kidnapped, Harry's lost glasses become a crucial element for his escape. Maybe the kidnappers don't realize the magical properties of the glasses and Harry uses a spell that is activated only when his glasses are in a certain state. For example, he could have a spell on them that when they are broken in a specific way, it sends a signal to his friends at Hogwarts.
In a fanfiction like this, the plot might involve Harry being kidnapped by a group who wants to use his fame. Without his glasses, Harry is at a disadvantage. However, he discovers that he has latent magical powers that don't rely on his sight. He starts to learn to use these powers to outwit his kidnappers and eventually escape, finding his glasses along the way which he then uses to fully restore his normal magical abilities.
A plot could revolve around Harry being kidnapped by a dark wizard who steals his glasses as a trophy. Harry then has to rely on his other senses and the help of some unexpected allies. The allies could be magical creatures that are immune to the dark wizard's magic. They guide Harry through the kidnapper's lair, and in the process, Harry discovers a way to magically summon his glasses back to him, which gives him the upper hand to defeat the kidnapper.
Perhaps in the fanfiction, Harry is kidnapped by a powerful magical creature that has a vendetta against wizards. When it grabs Harry, his glasses are knocked off. The creature takes him to its underground den. Harry, without his glasses, is at a great disadvantage as he can't see well. But he remembers the magic within him. He tries to communicate with the creature using Parseltongue (if it's a snake - like creature). He hopes to either convince it to let him go or at least find his glasses so he can better defend himself and find a way back to Hogwarts.
One possible fanfiction could be set during a fight with some dark wizards in a back alley. Harry is outnumbered and gets beaten up badly. In the chaos, his glasses are knocked off and broken. He has to rely on his other senses and magic to fend off the attackers until help arrives.
A fanfiction might have it that a new dark force in the wizarding world targets Harry. They manage to trap him in an old, abandoned manor. They torture him using various dark spells, and during the chaos, his glasses are lost. Harry endures the pain and tries to remember some of the spells Hermione taught him for self - defense. Eventually, he breaks free from his bindings and starts looking for his glasses. He stumbles around the manor, using his wand light to search, while also being on the lookout for the return of his captors.
One such fanfiction could be 'The Dark Trials of Harry Potter'. In this story, Harry endures intense torture by dark wizards which causes him to lose his glasses. It shows his struggle to survive without his vision aid while facing the evils. However, such fanfictions often deviate from the original J.K. Rowling's vision, but they can be interesting to explore different aspects of the characters.
One possible plot could be that a dark wizard kidnaps Harry Potter in order to steal his powers. In the chaos of the abduction, Harry loses his glasses. Without his glasses, he has trouble seeing clearly which adds to his vulnerability. The wizard might be working for Voldemort or could be a new enemy. His friends Hermione and Ron would then embark on a quest to rescue him. They would face many challenges along the way, like getting past dark magic traps and finding the location where Harry is being held captive.
One possible plot twist could be that without his glasses, Harry has a hard time recognizing his captors. It might turn out that they are people he thought he could trust, like some seemingly friendly Hufflepuffs who are actually under the Imperius Curse. This would add an element of betrayal and confusion to the story.
One possible plot could be that Daria is kidnapped by a group who mistake her for someone else. In the chaos of the kidnapping, her glasses are lost. As she's held captive, she has to rely on her wits more than ever without her glasses to see clearly. She might start to analyze her captors' behavior and motives, trying to find a way to escape. Maybe she uses her sharp tongue and intelligence to outwit them, all while dealing with the inconvenience of not having her glasses.
One possible plot twist could be that without his glasses, Harry has trouble recognizing his captors or his surroundings clearly. This could lead to some miscommunications or misunderstandings. For example, he might mistake a friendly wizard trying to rescue him for another captor. Another twist could be that the kidnappers took his glasses to specifically weaken him, as he is so used to seeing the magical world clearly with them. They could be using it as a psychological tactic to make him feel more vulnerable and off - balance.
A plot twist could be that Harry's kidnapping and loss of glasses is the result of a time - travel mishap. A future version of himself (or someone else) accidentally causes the present - day Harry to be kidnapped and lose his glasses. The future version is trying to change the course of events for the better but ends up creating chaos in the present. Harry, without his glasses, has to figure out what's going on and how to fix the time - line while also escaping from his kidnapper. Another twist could be that the kidnapper is actually an undercover Auror gone rogue who is using Harry as a bait to draw out a much larger and more dangerous criminal organization. Harry's glasses are lost in the process, and he has to figure out who to trust among his captors.
One possible plot could be that without his glasses, Harry discovers he has a new magical ability related to his vision. Maybe he can see magical auras more clearly and it helps him in his fight against the dark forces. For example, he can easily detect hidden Death Eaters by the color of their auras.