I don't know that they'll run into each other at the party since Thor is distracted by food and his centuries-long unrequited crush, and Sif is pretty much avoiding him.
BUT!
We can do a thread set after the party. Maybe it's time for Thor to figure out that Sif is still living in his hall. I think that would be hilarious, actually, since he's completely missed it up to this point. Or we can do something in HDC, either dramatic or sweet... we can do his courtship of her, or we can do after he gets the brain injury, or we can do after he finds out about Loki. Your call, lady. What appeals to you?