If their work place was a normal stop of mine and I see them often yeah maybe I would ask what's up to clear the air, don't want things to be awkward which it can be if there is nothing left said between the two when someone makes a move especially if that's a regular spot for me, might make it seem like I'm stalking them if I never have a discussion about it.
I've personally had many men (and a few women) give me their number while I was at work, I either graciously accept it and tell them we can be friends or I tell them I'm not interested, or I have a bf or something along that lines and I've never once had a sour reaction. It's a part of being bold, they are bold enough to hit you up, they are big enough to get rejected. I'd be more afraid of the guy that came in every day and watched me work, sitting silently in a corner and tried very hard to make small talk with me at every opportunity. Those are the unpredictable ones.
The ones who are honest and upfront don't want to waste time.