... Will you receive something in the mail notifying of a judgement against you... or can the creditor just get a judgement against you... and garnish wages and/or bank accounts without you knowing...

NOt normally, they must attempt to serve you with summons to appear in court. Some dishonest debt collector try to get around this process by claiming the attempted to serve you but was return.

You have a right to defend against their claim.

You can visit your local court and ask if anything has been file under your name.