The transaction made by the OP seemed legit to me even though he paid the seller using bitcoin. It is possible that the OP did not mention payment via bitcoin on the proof of payment [transaction receipt] because he knows that bitcoin is illegal as a means of payment in his country. This allows him and the seller to sign a receipt with the estimated value of the payment in fiat instead of bitcoin which is not legalized by his country's government.
He has option with payment proof use price bought plot of land measuring after converting with bitcoin values without have use 1 bitcoin as payment proof, I think if country still not allowed using bitcoin as legal currency transaction when get problem he has chance losing plot of land measuring bought. But if both of them are trusted is not worry what ever payment currency kinds use for transaction but at the future we don't know about seller looks trusted or not. But for keeping plot of land measuring better change name and he use his name take care about what happen at the future later.
In my nation (and I am guessing for OP as well) there is a good chance that you could have a law that says as long as there is an agreement, anything could be used. Like for example you could give 100 cows and get a land, and yes that is barter we used thousands of years ago, but it still works even today.
This is why I believe that we should not be focusing on the part where if it is legal or not, but the part how he used his bitcoin income on something that is tangible. Is it a better idea? I do not know, if he can turn a profit then it is a great idea, but if you ask me I would have stayed in crypto because I do not know much about any other business to be fair.