Was it a brand new bubble mailer or one that had been previously used? The reason I ask is I occasionally receive chips that are mailed in a previously used bubble mailer and sometimes the padding properties of the mailer are greatly diminished and they aren't much better than a regular envelope. Considering that you also used airtights, it would appear that the buyer must have broken the chips somehow. I can see one of the chips breaking but not both. Your hands may be tied by eBay as to what your response can be but if the buyer cannot produce the packaging material, I would tell him or her to go pound sand down a rathole!!!