Oupa-

The seller had the rifle listed on two different venues.
Corbin contacted the seller via gunsamerica, which is essentially an online classified ad on the web.

meanwhile the seller still had the rifle listed on gunbroker, the auction site.
The deal was made between Corbin and seller. Later on the seller -who should have shut down the auction (shouldn't have had it listed on GA and GB simoutaneously in the first place)- gets an email from a GB buyer and drops the deal with Corbin

Big pile of bullshit on the behalf of the seller.
The seller screwed up and won't honor his word with respect to Corbin's deal.

Seller has no integrity.

--Tinker