No loan is granted on Xerox copy futher he cannot sale the property based on these xerox documents because you are legal heir to the property and actual owner.
Give lawyer a written notice to return the property Xerox papers.
Also the buyers responsibility to purchase the property under clear title so in worst scenario even if he did something wrong that can be reinstated in court and that document can be cancelled and he can be charged of fraud forgery cheating.
Also in future If you give Xerox of any document identity proof or property papers to anyone mention the reason on Xerox of giving such papers and mention date.
Don't worry the clear title and the real owner is required to register the property on verification sale or any deed is executed.
Check the municipal record for your satisfaction hire a good lawyer get property mutated in your name