I'm sure people who work at the reference desk more regularly than I do have had this happen to them plenty of times before, but the Unshelved comic for today reminds me of one particular experience at the reference desk I had. I don't know how much of it people retain, but I usually try to make sure that I talk about what I'm doing as I do searches for people - maybe they're actually paying attention, maybe they're not, but usually they at least stick around and look like they're paying attention.
This one particular time I'm thinking of, the person didn't even do that. I started to do the search based on what they first told me when they walked up to the desk, looked up to ask for some clarification on a few things, and saw them walking away to go sit at one of the computers. Which automatically made me think, "so, what am I, the research vending machine?" I managed to get the guy to actually come back to the reference desk (I also offered to help him do stuff at his computer, on the off chance he was worried he might lose his computer to someone), and then I found out that he was actually part of a two-person group. The second person stuck around with me to watch me search and clarify things as I searched, and the first person walked off again.
I wonder how common this sort of thing is? I had never had someone come up to me before, tell me what they were researching, and just go to a computer while I was in the middle of searching databases for them.
I can't remember at what time of year this happened. Maybe it's more common during finals time?