Legal Question in Wills and Trusts in California

The only way would be finding information in the papers of the deceased indicating they had worked with a particular attorney, or calling around to all the reasonably likely possible attorneys in the area and asking. There is no database of estate documents, and in fact they are very private. If an attorney knows a trust client has died, they will usually contact the trust beneficiaries, but there is no guarantee they will know about the death, and there is not necessarily an obligation to do so.

If you have an idea of when the trust was done, it might be helpful to review bank records for the time period and see if you can find a payment to a lawyer.