Tell us what do you have in your hand ? Registration must be in the car all the time. Look at the registration it has only your friend's name then he owned this car if not some one else owns it. You have to act differently in these scenario.
If he owned the car : he should be able to give you singed title at the time of sale. Do you have any written information like bill of sale? A signed check?
If it is owned by a dealer :this is not your car until you pay in full. And you need to transfer it from dealer to you name, Dealer has the title.