after i dropped down to the explorer card from the club card, i bought a few one time passes on ebay "just in case" i needed them for domestic IRROPS. the club agents seem to be a lot more helpful than others in most airports.
i went to scan one at the BOS UC, and the agent said that the pass had already been used. i have no reason to suspect otherwise, and she even scanned the barcode a few times. no dice.
i don't understand how it happened in the first place. i've never seen an agent give back a one time pass after it has been redeemed. the pass looked identical to others - same card stock and perforations, so i don't think it was counterfeit. i would have filed an ebay/paypal claim, but i wasn't sure which seller sold me that particular pass.
that being said, i'd do the following when buying passes on ebay: (1) write down the seller's username on the pass upon receipt, and (2) try to use them within 45 days after purchase so that you're covered by paypal (passes with shorter expiration dates are cheaper anyways). it would be entertaining to file a chargeback with chase for one of these.