if you can’t find him during lunch, then try looking for him during free time or when you skip class in the locations specified. there’s a very good chance you’ll find him eventually while skipping class as you only have 1 class with him, so i recommend building up on BAD and skipping frequently. that’s how i initiated most of his events after my second interaction with him.
as for how i got the second interaction, it might’ve been luck, but i literally just chose his icon when it was time for lunch and it initiated it for me. when i did, it took me to the garden, so maybe try going there more often?
if you’re still having a hard time finding him after doing his first interaction in s.o.m then it might just be the rng messing with you atp :’) or your game is bugged, this has been happening to a lot of people tho so if in doubt, just reinstall