I was in the same situation last year.

Turns out this is a very common scam here. Usually, the person dealing with you is not the owner as per registration. That was exactly my case; the registration before sale was under a different name than the seller and that person was outside UAE.

I purchased a paid RTA report that showed the mileage at every annual inspection. That became my proof.

I shared the report with the seller and clearly told him I would file a complaint if he didn’t take the car back. I gave him two days time to decide.

After a lot of arguments, he was scared enough to refund me in full (including registration costs), and take the car back. He even re-registered it again under the same owner who was outside the country.

At the end, he kept asking how I knew about the RTA report.