Even if dealers tell you that all incoming firearms are sold, I would still maintain contact with them. Unless all the firearms have been prepaid in full, there is usually someone who, at the last moment is unable to come up with the complete payment. Cash is king.
I would at least maintain contact, and ask to be put onto a waiting list in case someone does not follow through on their purchase. Then you could slip into the one that suddenly becomes available. If they are all pre-paid in full, only a fool would say keep the merchandise I have already paid for.