[elephant007]

Just because the last place you used your credit card was Android Market doesn't mean that it's the place where your credit card number was taken from...
Credit/Debit cards are contently being attacked by thieves. The chances are just as even that your number was taken that way as it was from Android Market

If I were you I'd do the following
1. Cancel your current credit/debit card
2. File a police report with your local police department

Thanks for letting us know!