Legal Question in Real Estate Law in California

Sure, this is possible. A deed of trust is a financing instrument, given to secure a loan. Ordinarily, the trustor (maker) of a deed of trust must have some ownership interest in the property at the time the deed of trust is executed. However, the trustor might subsequently transfer his/her/their/its ownership, and this could happen with or without the permission of the beneficiary of the deed of trust (the lender). It is also possible that an error has been made in the recorder's office, either by the recorder's personnel or by your title-searcher. Mis-filing and sloppy title searches do result in mistakes. Also, it is possible for a deed of reconveyance to have been neglected, delayed, mis-filed or missed during a search, although I'm not sure how this would result in the situation you describe.

The name of the person who signed the deed of trust is not dispositive of ownership. A deed of trust is the document used to secure a loan, and can be signed by less than all owners (rare, but possible) or could even be signed by previous owners.