[That would be recognition crossing his expression, surprised if a little jarred himself. Yep. Now it got super awkward. He drops his hand to rest on the bar.]
I uh... [Clearing his throat.] Your blood. I'll be back with that.
[And so he wanders off and returns shortly with just that, setting it on a napkin in front of him in a nice glass. A little awkward silence goes here while Sam tries to find words to make this less weird.]