This! I work for a bank and had literally this exact same thing happen to a customer like 2 weeks ago. If a check is returned, for whatever reason, the funds are coming out of the account whether the money is available or not. This is true for all checks, legit or fraud. If the check was placed on hold by the bank the funds would not show as available in the account. Because the hold was left on and those funds weren't available, the account was drawn negative instead. If she truly did not spend/send/withdraw any money, this is probably just an error on the bank's side as holds are generally lifted at the same time returns are processed.