Can a collector collect a debt that is 12yrs old and had a co-signer with? Should they go after the co-signer?

I had a loan for a truck and my boyfriends parents co-signed for me and him. My boyfriend and I broke up and he took the truck. The bank contacted me to pay the debt and I told them to go after the co-signer as their son has the vehicle. Never heard from the bank again. That was 12yrs ago. Present day I got a letter from a Portfolio Management claiming they bought the account from the TD Bank. I had no recollection of it cause it was sooo old and they couldn't tell me about it either. Today they call me and tell me it was a loan. I told them I had a co-signer and they should go after them, and plus the debt is 12yrs old. They threatened to call me everyday.