He probably had trouble seeing clearly. In the wizarding world, even with magic, not having his glasses would make it hard to recognize people from a distance or read small details. For example, in a Potions class, he might not be able to read the fine print on ingredient labels or see the exact color changes in a potion as it brews.
He might start by retracing his steps. He would think about all the places he had been recently and search those areas thoroughly. For example, if he was in the library before losing his glasses, he would go back to the table he was sitting at and look around on the floor and on the bookshelves.
One big challenge would be in his studies. Magic often requires precise wand movements and seeing spells being cast by others clearly. Without his glasses, he could misinterpret what a teacher is demonstrating, and this could affect his learning. Moreover, in Quidditch, he would have a hard time seeing the Snitch or other players clearly, which is crucial for the game.
One popular fanfiction might be about how James Potter's glasses became a magical heirloom. Maybe they were passed down through generations and had special powers that only the Potters knew about.
In many fanfics, James Potter's glasses are often used as a symbol of his intelligence and charm. They can also be a way to show his vulnerability, like when they get broken during a fight, adding a touch of humanity to his character.
The plot could progress with Harry using magic to compensate for his lack of glasses. For example, he could use a spell to make his eyesight better. Or, his friends could use their skills to help him. Hermione might use a spell to locate his glasses in the chaos of the brawl.
In such a fanfiction, Harry might be at a serious disadvantage. Without his glasses, he'd struggle to see clearly. His opponents could easily take advantage of his impaired vision. He might have to rely more on his other senses, like his hearing or his magical intuition. Maybe he'd cast a spell to enhance his vision temporarily, but it could backfire or be disrupted during the brawl.
Well, his eyes. His eyes become a more prominent feature. In some fanfics, his eyes are described as having a sort of magnetic pull without the glasses. For example, Lily might notice his eyes more and it could be a factor in their relationship development.
One great fanfiction could be 'The Unseen James Potter'. In this story, without his glasses, James is portrayed as more mysterious. His hazel eyes are more noticeable and seem to hold a different kind of allure. The story might focus on how his appearance change without glasses affects his interactions with others, like how Sirius and Remus react to this new side of him.