Was the missing serial number visible in any of the posted pictures in the ad?
Yah right, someone left it an Uber, and you believed that? Did you check the sellers previous activities/history?
I recently purchased a XPR7550e on eBay. One seller stated that he had several brand new units in a box but did not list any of the feature sets for the radio. So, I sent a contact email to him asking the question and never received a response. Either he didn't have a clue on the question I asked or he didn't get the contact email or sold them all. Regardless, I didn't wait very long for his response and went to another seller for the same radio that listed all the features and had a great history and I have had good luck with him and his protects from previous sales.
It appears the the seller that didn't respond either pulled his ad for the several new radios in the box and sold them all or wasn't legit.