I just can not get over the fact that Dean’s reaction to Daphne wasn’t “Atta, boy Cas!” *smirk, wink*
Now maybe because of the somber circumstance, (you know just finding out Cas is alive and all) maybe it would be a bit toned down…
But still… I would expect from Dean, something like a brief brow furrow, ‘How did Cas manage that?’ Followed by a head tilt/nod and sturgeon face, ‘Good for you buddy’. Or something like that.
Because that’s just what we’d stereotypically EXPECT to see when a guy’s best friend loses the v-card.
Especially since this is DEAN. Stereotypical alpha male Dean
Let-me-take-you-to-a-hooker-and-get-you-laid-Dean.
Especially considering how Dean acts when Sammy gets a girl “That’s my boy!”
INSTEAD Dean’s reaction is this:

He sucks in a quick, hard breath and swallows.
It looks as though, it feels to Dean like a punch in the gut.
Like it never even occurred to him that this sort of thing could happen. That someone else could call Cas theirs. Because Cas has always been Dean’s. Cas’ entire existence was centered around Dean.
And maybe this was something Dean needed to see. Because sometimes you don’t know what you want til it’s gone. Cas dies and Dean realizes how much he misses Cas. Dean sees Cas belonging to someone else and he realizes how much he just wants Cas to be only his.
Dean is not that dumb. He isn’t be so blissfully ignorant of his own feelings that he doesn’t understand why it upsets him to see Cas with Daphne. He might be just now realizing it… but after that little display, trust me, he knows.

Lol, obvious fishing for details is obvious. This question feels so much like the classic “So.. are you seeing anyone?”

Dean: Oh great. Fine. more flirting.That’s cool. NOT

I also think maybe THAT’S why Dean was so quick to get the fuck out of that hospital, because he’s running away from these feelings about Cas, which are possibly very “new” (in that he’s just now getting it) and also maybe somewhat confusing to him. Emotional crisis. Run!