At this point there are a couple things that I think the party seems likely to do at this point:
1. Ask the slaves to show you where they were kidnapped.
2. The watchman mentioned that "I recognize the seal on the bottle. It's wine from the Trouscan Estates. Odd; it's imported and they usually only sell their stuff at a few waterfront inns." So the waterfront might be a good place to check out.
And of course
3. Pay for your drinks
Which will it be?
Well, I'd presumed we'd be doing (3), since we don't want to be in any more trouble than we're already like to be in.
Then I'd think (1) would be the most direct choice, since it's less roundabout than wandering about trying to track down the wine, which we can always come back to later.