The creditor should repay the money garnished, as the garnishment is a violation of the automatic stay imposed by the bankruptcy filing.
But when the cash is returned by the creditor, the money becomes property of the bankruptcy estate (unless it is exempt) and can be used by the trustee to pay the debtor’s creditors.
The trustee should take action to seek the return of the money garnished.
If the trustee does not take action, you may be able to ask for the return of the money — again, with the understanding that the money may have to be paid over to the creditors.
The bankruptcy schedules permit you to list whatever garnishments may have taken place against you. If this particular garnishment was not listed in the schedules, the debtor may wish to disclose the garnishment to the Trustee at the 341 meeting of creditors.
For these and other overviews and instructions for managing a pro se Bankruptcy filing, see the Standard Legal Bankruptcy legal forms software package.