Another place to check is FanFiction.net. There are many Harry Potter fanfictions there as well. You might need to do a more in - depth search, but if you look through different categories and use the search bar with the right terms, you may find some great 'Harry Missing' fanfictions.
There's also 'When Harry Vanished'. In this fanfic, it delves into the chaos that ensues in the wizarding world when Harry goes missing. It shows different perspectives of various characters, from Hermione's frantic research to Ron's impulsive actions to try and find their best friend.
Harry Potter himself is a very likely character to be missing. He's the central figure in the series, and his disappearance would create a huge upheaval in the wizarding world. His friends would be desperate to find him, and the whole Hogwarts community would be on edge.
One place to start looking for the missing fanfiction could be on large fanfiction platforms like FanFiction.net or Archive of Our Own. They have extensive collections of Harry Potter fanfictions. Check their search functions, maybe filter by characters (Snape and Harry Potter) and relevant tags.
One interesting 'Harry Potter Missing Moment' in fanfiction could be the time between when Harry first discovers he's a wizard and when he actually goes to Hogwarts. Fanfictions might explore his initial reactions, how he tried to cope with the sudden change in his world view, and his secret attempts to practice magic before getting his wand. Another could be the moments during the Triwizard Tournament that we didn't see in the books, like the behind - the - scenes discussions between the champions or how they prepared in private.
You can try some well - known fanfiction websites like Fanfiction.net or Archive of Our Own (AO3). They have a vast collection of Harry Potter fanfictions. Just use the search function on these sites and type in relevant keywords, like the characters you're interested in or the specific plot elements you're looking for.
One possible fanfiction could be that Harry loses his glasses during a Quidditch match. He has to squint to see the Snitch, which leads to some comical near - misses and some very frustrated team - mates. In the end, he manages to find his glasses just in time to catch the Snitch and win the match.
It could be a new dark wizard that we haven't seen in the original series. This wizard might be jealous of Harry's fame and power and wants to eliminate him by making him disappear.
One possible plot could be that Harry has been kidnapped by a dark wizard who wants to use his powers for evil. Another could be that he has run away to find a way to defeat Voldemort on his own without endangering his friends. Maybe he's lost in a mysterious magical realm while on a quest and can't find his way back.
Well, it could be that the sister was kidnapped by dark wizards when she was a baby. Years later, Harry discovers some mysterious clues that lead him to believe she might still be alive. He then embarks on a dangerous journey to find her, facing many magical obstacles along the way.