Most Helpful Guy
Maybe his girlfriend was at the party... It sounds like he was not ready to announce to his friends that you two were dating. He may have wanted to keep it just between the two of you for a while and see how things went before letting anyone else know. Or he may have been interested in another girl there at the same time. Or, he may not really be interested in you and was simply being polite during the date. Either way, if he is embarrassed to be seen with you, drop him.
Most Helpful Girl
He didn't want to let it be known that he knew you because his friends were there m
Perhaps he wants to get to know you better before he let's the two words intervene.
I would ask him about this.
I'm sure he will be willing to tell you.