I just found out from my x that he got a new car but my name was still on the old one and I never signed any paperwork when he traded it in. How can a car dealership do that with my name still on it?
In general the purchaser could not get the title in their name unless the title could be cleared.
When there was a loan on the vehicle there were three names on the title: You, your-x and the bank.
When the loan was paid the bank released their lien against the title.
There are a couple of ways your name could have been removed:
the divorce decree divided the assets. And the settlement papers directed that your name be removed from the title.
At some point you signed a quit claim deed. The deed told the world you were giving up your rights.
some sort of fraud.
If the fraud was done in person at the DMV or the dealer, they would have wanted to see and make a copy of the drivers licenses. If 'you' weren't there your-x would have needed to present a notarized document that would meet the requirements.
So check the divorce/settlement documents to make sure they don't include a copy of something directing DMV to remove your name. If you can't find it, talk to your divorce attorney for advice.