Me to writer sending in revised full ms: Hey, you should get that YOUR TITLE (THE FIRST DRAFT) off Amazon.
Writer to me: Thanks for the notice. I printed some reading copies of that draft for close friends; I guess one of them sold me out. :P
Me, looking at Amazon listing again: Wow, you're right. This is offered by someone clearly not you.
Me, looking at Amazon listing an hour later and no copies are available: Aha, you bought the only copy.
It never occurred to me that friends would sell what is essentially a bound manuscript.
Which brings me to the point: when you print up your book and hand it around to your friends for comments, or feedback, OR you just hand it out for giggles, you're giving someone an edition of your book and they can sell it on Amazon. If I'd been just skimming while researching a query, I would have assumed the book was published already and said no. Obviously I should do more than skim, but you should also be aware this can happen.
PS I don't think this was done by a critique partner. The manuscript was printed and bound and sent to friends just as a "hey, look what I did" kind of thing. I'm still quite confident your crit partners won't do this kind of underhanded thing.