Nick was there, bartending a good part of the night so drinks weren't too heavy to start. But then he goes and disappears with Sabrina and comes back at her side, and it's maybe possible to tell his mind is elsewhere. When Sabrina finds other people to hang with he spends his time going back and forth between her and the bar.
He also spends time talking to Hazel who is distracting him from drinking more than he should while also keeping him entertained at the bar.