How to validate authenticity of 32GB micro sdhc card

has anyone bought from a Amazon Marketplace seller McTechy?  Profile can be found


HERE

I bought a 16 GB microSD card for $11 and thought at the time that, gee, prices sure have dropped.  It worked fine for the last three weeks and then, boom, now its all messed up.  I’ve been using it with my Sansa Clip+.  Oddly enough, it can still be read just fine with the Clip+ but cannot be recognized directly from my desktop computer or any of the two laptops I’ve tried it on.  I’ve attempted using different card readers and no go.  I attempted reformatting with the app SDFormatter, and it either gets stuck or won’t even see it.  The application H2Testw also will not see the card.

There is a serial number of some kind, barely readable with a magnifying glass.  If I photograph it and get the number on it, will SanDisk help me out?  I would like to send this Amazon seller a message saying “hey you sold me a POS card” but it would carry more weight if SanDisk could confirm for me that it’s not legit…