Isn't the deed that was executed with the sale going to describe exactly what was sold?
Some do, some don’t but even with that we have the other issues that show the seller had no intent to sell the barn.
While the op should prevail, imo, getting to that end may not be simple, or cheap. Of course I’m not privy to all the details of the issue so anything I say is only based on what I’ve read here.
As to a warranty deed. From Cornell school school of law:
A type of deed where a
grantor guarantees that the grantor holds clear title to a parcel of real estate and has a right to sell it to the
grantee.
It does not warrant the title to be correct. It warrants that all land described is owned by the grantor and warrants the grantor has all rights to transfer said land. In other words; seller warrants there are no other claims against the land at the time of the transfer.
One thing not mentioned is: was the seller aware of the true property lines? Maybe the statement he is not selling the barn is based on his belief the barn was in fact on the lot he retained. If true, that furthers the boundary by agreement arguement.
Simply put:
Each party agreed what was being transferred even though they weren’t aware the description did not detail the lots as the parties believed.
As I said; I’m not saying it will go one way or the other. I see arguments on both sides. If the parties cannot agree to settle this between themselves, I can see it becoming quite costly with no clear winner other than the lawyers.