Free month of groceries

I went grocery shopping this morning. Total bill 330. I had my food stamp card. It seemed to have went through okay but when I checked my balance later, it wasn't anything removed for 330. I call the store and ask to speak to the manager and tell him my groceries weren't paid for.
He said there wasn't anything wrong with his food stamp system and that if i had an issue, to call the state. He didn't even seem interested to look up the transaction.

I am sitting here with 330 worth of free groceries. Should i just shut up and count it as a blessing? I do feel kind of bad as the food was never paid for.