I think many of us can agree that Dean didn’t seem like he had had a night of awesome sex in 11x04, and his “Mistakes were made” comment was rather interesting. Here’s my suggestion about what happened in the roadhouse: Dean doesn’t find Heather so he just sits at the bar, chatting up people and getting increasingly drunk. Then some really sappy and sad love song starts playing and his thoughts finally turn to Cas, subject he has been trying to avoid that night. Getting more and more drunk he finally starts pouring out his heart about his sexuality crisis to pretty much anybody who will listen, rambling on about his non-straight feelings for "a friend" (maybe he even cries a little). By morning at least half of the roadhouse knows about Dean's feelings for “some Cas”.