Sorry that I didn't see this question earlier.
What could happen is that the DMV could turn the papers over to the prosecutor and you could be charged criminally with fraud and with some form of perjury for providing false information on a government document. In order to meet his burden of proof on something like this, the DA would have to show that you did this intentionally. If a jury believes you may have made a mistake, that's reasonable doubt and you could not be convicted of the charges.
Perjury is a felony in California, but the DA would have discretion, first of all to decide whether to bring any charges at all and, secondly, to determine how he wishes to charge and dispose of the case. The worst case scenario on a plea agreement is typically probation, but I'm not suggesting any plea. I'm merely letting you know that jail or prison would be unlikely if at any point along the lines you were looking to cut your losses.
The best case scenario is that the DMV investigator decides this was a mistake and simply assesses you the taxes you would have had to pay to transfer the title correctly.
No news is good news, so don't bother the DMV about this. The longer the time that passes without you hearing anything official, the better the chances you never will. You should think about consulting with a local criminal lawyer, just in case. You don't have to retain him now, as there's nothing for him to do, but when there is no emergency need for a lawyer is a good opportunity to take the time to find a good one, just in case.