We're seeing this from OP's POV, remember. Maybe the delivery guy decided to slid a note to ask whether the GF was okay because he thought she could be in an abusive relationship.

Look at it from the delivery guy's perspective. When you deliver at that address you usually get a girl answering. This time a man opens, and when you ask where the girl is he flips off. He then forces you to leave and threatens you.

You have admit that it could look like an abusive relationship, so the delivery could have acted with a good heart. We'd have to know what the delivery guy wrote in the note to decide (word by word), but OP wrote in a comment that he doesn't remember the exact wording.

And I'm telling you this as a woman, who has to worry about creeps. If the delivery guy was trying to check on her, there would be nothing wrong except for OP's reaction to the whole situation.