I don't even use them

Hmm

Oh..shit

You don't use them, but your BOYFRIEND found them?

What are they actually for?

That's how my step-grandma found out my grandpa was cheating on her. She only used a certain brand of bobby pins and she found one in his car that wasn't that brand.

Ooh gurlll he's cheating

They just appear wherever women happen to be, it doesn't matter if you bought them or not.

Oh you poor thing

He could have given a ride home to some other woman (innocently).
It could belong to his sister or mother.
It could have come from one of HER frinds and found its way into her pocket.

I mean, I think it's highly unlikely that you wouldn;t even have a single bobby pin in your possesion.