Contract Formation without Consensus Ad Idem

Arre yaar, most of us think we know contract law, but this question is a trap. The problem is about X and Y who agree to buy and sell a house through a broker. In the agreement, they mention the house's address as "123 Main Road." However, there is no such house, only a plot of land on "123 Main Road." The plot is worth 50 lakhs, but X and Y agreed on the sale price of 1 crore. In such a scenario, is there a contract between X and Y? Most people will say yes, but remember, a contract requires consensus ad idem, i.e., a mutual agreement on the subject matter. Here, the parties had a mistake of fact, a plot instead of a house. We all know this is a contract of sale, but is it a valid contract?