How to get a deed of trust corrected?

I bought 2 parcels of property in 1997 from the same people. Property with house was a deed from the wife and property with shed and barns were in deed from the husband. When I closed on the transaction, to save money, we closed on both properties together. And the County Tax Appraisal district had 2 separate properties listed because we paid taxes separately.
In 2006 we got a loan on the property with the house on it. We had appraiser and everything. His dimensions were for just half of the property. And the loan was made. In 2011 we got foreclosed on. We still paid property taxes on the other property with the shed and barns on it for 2 years. And when the mortgage company foreclosed, they only picked up the taxes due on the property with house on it. So everyone knew it was 2 separate properties. In 2013, I found out the Tax Appraisal District just erased the boundary line between the two properties and combined them without notifying anyone. The people that bought the house even admitted they only bought that one piece of property.
How do I go about getting this piece of property back? It was 2 separate parcels for a LONG time and all the sudden the tax office combines the two.
Please help
Added (1). The mistake actually happened when the loan officer gave the paperword to the title company to draw up the deed. He was suppose to go by the appraisers dimensions and draw up a deed where it was just that one parcel. But the guy from the title company just faxed a copy of the original deed that has both parcels together to the courtesy closers. And that was it.

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