Well, without actually reading it, it could be about a girl who was somehow important to Tom Riddle but then lost from his life. Maybe she was a love interest, a friend, or someone who had an influence on his path to becoming Voldemort. It might explore their relationship, what led to her being 'lost' and how Tom Riddle was affected by that loss.
I'm not sure specifically as I haven't read this fanfiction. But it could be that the girl was a source of light or goodness in Tom Riddle's life. Her loss could have been a turning point that pushed him further into the dark arts. It might show their interactions, her attempts to save him perhaps, and then her disappearance which led to his further descent.
The fanfiction 'the girl tom riddle lost' might revolve around a complex relationship. The girl could have been a classmate or someone he met in his early years at Hogwarts. She might have seen the good in him that others didn't. Her loss could be due to a number of reasons like she left Hogwarts, or something more sinister happened to her. And this loss could be what finally breaks Tom Riddle's last bit of connection to the normal wizarding world and sets him on his path to evil.
To find 'the girl tom riddle lost fanfiction', start with the biggies. Fanfiction.net has been around for a long time and has a huge library. Just type in the title or parts of it in the search box. AO3 is also great. It has a very organized tagging system. You can search not only by the title but also by tags related to Tom Riddle, like 'Tom Riddle', 'Harry Potter', etc. Additionally, you can ask in Harry Potter fan groups on social media platforms. Some fans might know exactly where to find it.
An old Harry Potter fanfiction about Tom Riddle could be about his time as a young wizard trying to gain followers. He was a very intelligent and manipulative character. Fanfictions might explore how he used his charm and intelligence to persuade other students to his way of thinking. Maybe he starts a secret club where they study dark magic together, which is a precursor to his later Death Eaters.
Typically, in 'tom riddle lemon fanfiction', there is often a strong focus on the character of Tom Riddle. The 'lemon' part usually implies some level of romantic or sensual elements. For example, there might be detailed descriptions of the relationship between Tom Riddle and another character, with a touch of passion.
His relationship with other characters is also a common theme. For example, how he interacts with Dumbledore or his classmates at Hogwarts. Some fanfictions also focus on his inner turmoil, the conflict between his human side and the dark side that is growing within him.
You could also create a fanfiction where a new character, an orphan just like Tom, arrives at the orphanage. This new character could either be a positive influence on Tom, trying to show him kindness and friendship, or they could be in competition with him for the limited resources or attention in the orphanage. This would add a new dynamic to the story of Tom Riddle in the orphanage.
Maybe it's a group of future Ministry of Magic officials who have become corrupted by power. They view Tom Riddle as an anomaly from the past and fear that his knowledge of old magic could disrupt their control over the wizarding world, so they become the main antagonists in his journey.
Tom's character could become more vengeful. Meeting his father, who may have abandoned him, could make him more determined to prove his worth and power. He might see his father as a symbol of all those who have wronged him, and this could lead to a more rapid descent into darkness.
One common theme is power struggle. Tom Riddle often has a thirst for power, and when he crosses over into other worlds or stories, he may face new challenges or rivals for power. Another theme is the clash of cultures. His own dark and calculating nature from the Harry Potter universe may contrast with the values and norms of the new world he enters. And identity exploration can also be a theme. As he experiences new things, he might question who he really is.
Power is a common theme. Since Tom Riddle is already a power - hungry character in the original lore, as a vampire, his pursuit of power becomes even more complex and dangerous.
One common theme is the struggle for power. Since Tom Riddle is known for his pursuit of power in the original lore, in fanfictions about his abuse, it often becomes a way for him to either seek revenge or prove himself. Another theme is isolation. The abuse he endures can make him feel alone, and this is often explored in the stories.