ID: Ask if the men mentioned anything about going to a hotel earlier.
"Hmm... I don't think so. I'm not really at liberty to discuss what my customers talk about, you know?" You take a sip of your water, looking at the glass before your eyes move back to him.
"What if I told you that this was a murder investigation?" As soon as you say that, the bartender looks taken aback - suppose that makes sense, it's not every day you get a murder investigation sprung on you!
"Well, uh, are you a police officer or a detective?"