so not really an intrusive thought but

have yall had someone who you have a crush on but chat with them occasionally (let's say once in 3 months) but because you like them you have a fantasy in your mind,you dont even know them that well but you have created a personality for them in your mind,you assume that they will have that particular behavior when they meet you.You never confess to them because you know that you'll face rejection,but you still have some hope that after some years when you get in college you'll magically meet them again and they will like you.

this is my case,it's been 3 years since the crush,never gonna confess,but they are still all over my mind.