If you buy something from another individual, and you have no receipt or bill of sale then you have little or no recourse to a challenge to ownership if the previous owner has one. Or...
Jimmy gave Bob $100.00 for a genuinely upscale audio system and later the police came to Jim's door looking for him and the item.
Bob had stolen it and when questioned he falsely claimed that he "heard" that Jim had stolen it and set Jim up for a fall.
It was in Jim's possession, and he had no bill of sale.
Out came the handcuffs.
Don't get caught in a situation where you can be charged for accepting stolen property.
Whether you knew it was stolen or not, you still can get arrested and charged with "Receiving Stolen Property".
A man bought a small boat
from another man and the bill of sale had no mention of a hull serial number, It just had the manufacturer name and the words "small boat".
The buyer went to register it because he wanted to put a motor on it he had a problem because he had no acceptable bill of sale
Scammed?
You can find recourse to a scam where you buy something that was sold to you under false pretenses, and you have a proper bill of sale.
Thieves and scammers abound so protect yourself.
When you get a receipt for an item ask for some
identification from the seller.
If you want to register any motor vehicle, you will need the VIN (number), hull number, serial number or whatever applies.
If you want to sell any item you can be asked for your bill of sale from the previous owner and the reverse is a good idea, as well.
Ask for the owner's bill of sale from the person he/she bought the item from to be sure that you aren't buying a stolen item.
Details of the condition of an item etc. that are only verbal between you and the seller are meaningless.
Put it on the bill of sale if you want the condition to be understood by both parties. Other wise it might be considered "As Is"