Since we don't know the details of Tim's story, we can only speculate. Moebius strips are often associated with concepts like infinity and unity. In Tim's story, it could be that the Moebius strip is a key element in a mystery. Perhaps it's a clue left by a character that leads to a discovery about the nature of the world in the story. It could also be used to show the interconnectedness of different elements in the story, much like how the two sides of a Moebius strip are actually one continuous surface.
Well, without more context about this 'Tim's story', it's hard to say precisely. But generally, Moebius strips are really cool mathematical objects. Maybe in the story, Tim uses the Moebius strip to represent a concept that defies normal expectations. For example, if it's a science - fiction story, it could symbolize a portal that has no clear beginning or end, or a time - loop situation where events keep repeating in a never - ending cycle.