Loan default I never heard of

I  received a voicemail from a debt collector and returned the call. It was mid western alliance and they said I owed them for a delinquent loan from 2012. The only thing he could give me was a loan number and said it had to of been me  and I need to pay it now or they will take further action. I asked who the loan originally was from and he said he doesn't have that information, does not need to provide it, and any judge would rule that I owe them money. He was very rude, kept interrupting me and eventually I hung up the phone. My loan number does not come up under Google and there is no other information that I can attain. I do not want to pay this and I feel I should not have to if they cannot provide me with who the loan was originally through and what it was for.  I cannot remember taking out any loan for $300, that would have made no sense for me to do that. This has to be fraud. Please help.

Matt