We had a deal with our son, when he went off to college last fall, that he needed to contact us (via text or email) a couple of times a week.
This was not just helicoptering in our case, the boy has autism and we need to touch base with him to make sure he’s keeping up, getting help when needed, etc.
Naturally, he totally ignored this, never once initiated contact, and would even fail to respond to emails from us when we had specific questions for him (which is just plain rude).
It’s conceivable that his roommate might have reported him missing if he’d disappeared but I doubt he had any other close-enough friends to do so.
Fortunately he’s just fine (though the failure-to-communicate etc. have led to his doing badly enough that he’s not going back this fall).