Don't know exactly on it works in Romania, but proving you purchased a patch of land is a different question -- for that you have the deed. You then submit the deed to the land registry. So this situation could at most result in the seller being able to sell the land more than once or disputes over the priority of sales over liens and other competing acts subject to registration.

You’re going to need more than just a claim to prove that, and anyone who did purchase land likely has some evidence in support, even if it’s testimony from others.

Only if you bought between the backup date and today

(And obviously has some doc to prove it)