Steam accounts who have their email changed/credit card changed are put on a 7 day trading restriction. If they didn't change the email, recover it. As always, if it involved money put it on a damn email account you can retrieve. Set it up with your phone number, have another email linked to it with a separate password
Other wise file a support ticket through steam, or I think you can call them for issues like this. Just have to do some simple things to proove the account is yours, probably be verifying your credit card, and they will give your shit back