Legal Question in Real Estate Law in California

There are various options, depending on what exactly the problem is. You don't describe it well enough for me to figure out what the exact issue is. The title company was probably acquired and there would be a successor, but that may be irrelevant. "two parcels are switched with parcel numbers" is completly unclear as to what the problem really is. So the solution could be as simple as recording a corrective deed, or it could require a quiet title lawsuit. Perhaps you should have your agents send me the question making clear use of land title terminology.

There are basically two paths the parties could follow.

First, and by far the faster, easier and cheaper way, is simply to swap parcels. A deed cannot be rescinded once it is delivered, but the result of the deed can be reversed by deeding the property (here, I guess, two properties) from whomever owns it now to whomever is supposed to own it/them. This plan requires that all the parties are in agreement and cooperative.

The other way is to initiate a lawsuit to "quiet title" or to "reform deed." This is obviously an inferior way, but may be necessary if there are uncooperative owners (or lenders) or one or more necessary parties cannot be found.

There is no particular need to find the original title company, unless you want to sue them for damages. They aren't part of the solution. Any lawyer or title company that understands how deeds and titles work can do the paperwork, if the parties are all willing to execute the deeds required to un-do and reverse the mistake.

One other issue to be concerned about is property taxes. If the parties voluntarily swap the properties, it would result in a change of ownership that will trigger a reassessment of the properties. That might be a good thing if the values are less than what was originally paid, but bad if values are higher.

In regards to the title company, contact the California Department of Insurance. Title companies insurance policies are transferred to other title insurance companies. If this was the mistake of the original title insurance company, your policy should still be valid with someone, and that title company should take the responsibility to correct the problem.