Depending on where the child care was done you would have given your mother a W-2 or 2099-NEC to document that expense if you wanted to claim child care credit. And she would have to have reported that income. If she reported that income you could tell the IRS that and that you didn’t know you needed to send her one of those forms. I don’t know if the IRS will accept that excuse but you have no other way of showing that you incurred that expense.
