I'm not a tech or anything, but I'm thinking, well, the piano has to be somewhere. If it had been sold to a customer, then it would instead be in a customer's house. There's no guarantee what conditions it would have been in - in a house (humidity control, kids or animals playing on it, or even a Lizt type pianist who (on the original vintage pianos) played pianos so strenuously that they fell apart.
As far as them having been played upon by pianist/customers trying out the piano while it sat in a piano dealer's showroom, I wouldn't think that would be much of any concern. Does the dealer have humidity control in his showroom? If he does, it's possible it's been under better conditions in the showroom than in someone's house. Not everyone pays attention to controlling home humidity levels when they get a piano as I mentioned above.
The one thing I'd be interested in knowing, however, is if the piano has been rented or sent out to be played in a concert hall. One of the pianos I played in New York City - was originally a beautiful mellow tonal quality. When I revisited it a few weeks later, I was nearly blown off the piano seat by both how much LOUDER the piano was, and also the mellow tonal quality was now extremely bright and cutting. When I asked about this I was told the piano had been sent out to be played at a concert and the hammers had been "juiced up". There was a small damage also to the cabinet which was going to be repaired. I later saw the repair which was excellent, you couldn't even tell anything had happened to it.
I think your question may be better placed in the general PW forum, or maybe even the technician forum. It would be seen by more PW members and receive more response. Most importantly, I don't see how this question fits into the category of "Forum Member Parties, Tours, Cruises & Meetings."
P.S. My husband says (tongue in cheek) what you could do, is go to Piano Fax and look up the maintenance records and see if it was in an accident.