Good afternoon Leroy,
I'm Doug, and I'm very sorry to hear of your situation. My goal is to provide you with excellent service today.
The problem that your friend has is that the gun is not abandoned property, and neither was it sold to him with the house, any more than a 5 year old Corvette in the garage would have been his to keep. While I understand that you would like to own the pistol for your collection, if it was stolen or reported as having been used in a crime and your friend sells it---without being the rightful owner, worst case scenario is that he could be charged with theft and sale of stolen property.
CA is in the top 5 of strict gun control law states and by your friend even trying to sell a gun he doesn't legally own, he is committing a felony. The smart thing to do will be to turn the gun over to police as a lost item which has been found and not run the risk of seeing what happens. As a former law enforcement officer and avid gun enthusiast myself, the things that come to mind when I hear of a nice handgun in a bag in the crawl space of a home is 1, it is a stolen weapon, or 2 was a weapon owned by a person not legally entitled to own a weapon.
I understand that you may be disappointed by the Answer you received, as it was not particularly favorable to your situation. Had I been able to provide an Answer which might have given you a successful legal outcome, it would have been my pleasure to do so.
If you have additional questions, you may of course reply back to me and I will be happy to continue to assist you further until your questions have been answered to your satisfaction.
Would you please take a moment to positively rate my service to you based on the understanding of the law I provided by clicking on the rating stars---three stars or more. It is that easy. That is the way I am compensated for having helped you.
Thank you in advance. I wish you the best in your future,