Relationships and finding closure

Hi my autism makes me very obsessive about things, whether it collecting something new or liking a guy.  There is a guy I used to go to school with who I still like and I have seen him around where I live over the last few years.  Over lockdown I did try make contact with him over fb and I did not get a response  and have been thinking what can I do get closure.  I thought about writing him a letter but I feel this wrong as it would have go to his work address. I just wish there was a way I could get closure on this issue and would like some advice?