I have seem about 3 "Mavic have been found" threads and no one ever comes forward. If you really want to find the owner contact the nearest DJI service center and give them the serial number. They can easily find out who purchased it and contact them.
I am not sure DJI could track every serial number back only the ones they have sold or when registered probably the email address used to register but due to data protection they wouldn't give that out so you would have to return to them I guess.
You're a good person for posting on here. A lot of people would not have made the effort. Thank you for being an honest human being. You could try contacting the FAA. If the drone was registered, they would have all the contact info.