Adrian knew he was the father weeks before this tragedy. If he cared about his child he would've found through a simple Google search the man that murdered him was a convicted child abuser.
Any parent who gives a poo about their kid doesn't just leave them with whoever, wherever.
Again, how would he have known about Patterson? The child was with his mother, correct?
If Peterson had any contact prior, it would have been with the mother and that's probably it. And even if he did met the guy before, why would he Google him, some random non-famous dude?