He's just supposed to go to market, purchase some food, and bring it back to his father so they can eat. It shouldn't be especially difficult. He's done it a hundred times before with no difficulty.

He gets to the market, reaches for the purse of coins his father gave him, and it's not there.

...He looks around for a guard. He's not really sure if a guard will be able to do anything, but this is the sort of thing you're supposed to tell a guard about.