Shop inhibitor

The opposite of a shop assistant. After sufficient interactions with an inhibitor, the customer eventually learns to steer clear in order to achieve a purchase. In fact, these people have such poor product knowledge and so little initiative, that one wonders whether they actually still receive a paycheck, or have lost their way home after the last downsize. Miraculously, products are still sold despite the inhibitor's best efforts to stem the tide.

Bob: Did you get some of those cool widgets?
Joe: No, I went there and they said they didn't have
Bob: That's weird, I saw plenty when I was there yesterday.
Joe: Well, I asked the shop assistant...
Bob: No, you asked the shop inhibitor. Next time, just look for it yourself.