Contact the police immediately. They will (hopefully) be able to give some direction as to who to report this to (the agency of jurisdiction will likely be the location where this deed was passed as being valid).
The problem you will have will be the time that has passed. You might have to show that you could not have reasonably known about the sale of the property until now. But, if you accepted payment or a share of the property before this, that argument will be hard to make.
Depending on the amount of money involved, it may be of benefit for you to speak to an attorney as well.
- Carl