Private Sales: Seller Didn't Finish Signing Title for Motorcycle and Drove Away with $5000

My question involves a consumer law issue in the State of: Oregon

Hello,

I have run into an absolutely huge problem. I was trying to buy a used motorcycle off craiglist and during my test ride the seller took all of my cash. He left the bill of sale signed and filled out, and also a title only partially filled out. It basically only has the sale price, date of sale, and one signature but it needs about 4 more. After I saw that he left with my money I have now tried many times to get my money back and give him the title back as well and motorcycle. I also suspect that the person who sold me the motorcycle isn't the person whos actually on the title. At this point I have no idea what to do. I'm a college student so I can't afford an attorney, he has my cash, and I can't legally ride the motorcycle, and the motorcycle needs $1000 in repairs. I am absolutely flabbergasted and lost with the situation and would really appreciate any help. Does having a partial title and filled out bill of sale help me at all? I don't have the sellers driver license, but I do have his license plate. Please any help would be appreciated it took me 2 years to save up all that money.

Private Sales: Seller Didn't Finish Signing Title for Motorcycle and Drove Away with $5000