I don't know whether you are technically required to file in California. But the sale will be reported to the IRS, which will pass the information on to the California FTB. In the absence of a tax return, the FTB will assume that the amount you received for the property is all profit, and you will get a notice from them telling you that you have to pay CA tax on that amount. So, to avoid trouble, you should file a return to show the loss.
