If you do, well, be prepared for the FTB computer in Sacramento to send you a love note.
How does the FTB know? Easy. The IRS has information sharing agreements with state and local taxing agencies. The first thing the FTB does its run the IRS return database with California addresses, expecting to find a matching California return.
If it does not, you will get a letter, telling you the FTB thinks you may have to file a return. Note: You may or may not have a filing obligation in California, but the FTB is simply asking. If you were a non resident of the state for that year, it is imperative that this be communicated to the FTB. Supporting evidence is always helpful. Some taxing jurisdictions will expect you to send a copy of another state’s tax return, but that is not required and in my view, provides “too much information”.
If you were required to file, well, they will welcome you with open arms.