Lucas and Derek
Despite being far more relaxed here than he was in Beacon Hills, Derek still had a fairly suspicious nature and he constantly scanned the crowd at gatherings like this to ensure that nothing untoward was happening. He noticed one man who was standing away from the others and whose eyes kept finding a woman who was barely visibly pregnant.
Concerned that he was some kind of weirdo stalker, Derek found himself shadowing the guy until he realized that he was picking up the woman's scent on him. It clicked into place that the woman he was watching was his mate and he was simply keeping an eye on her. He could completely relate to that.
"What's up?" he asked, deciding he should probably stop being a creeper himself.