The 4473 is a transactional record that shows the transfer of ownership from the FFL to the individual or other entity. It does not prove ownership, only tranfer from one party to another.
For the department I work for ownership of real property is generally accomplished via certain ways...title, deed, or some other "individually indentifiying" manner. The best manner is through the recording of some descriptive item on the property. For firearms this would be the serial number and a notarized statement from the complainant. A brief written description of the property and some individually identifying mark is generally all that is needed.
Real property is covered under a specific law called the Statute of Frauds. The is where items are covered by a specific contract. One may be wise to use the Statute of Frauds process to prove ownership of their individual firearm.
As far as the recoveringof your firearm after it is located post being stolen or used in the crime, the item is technically under the pervue of the the court having "original jurisdiction" of the case. Simply put, the police may not be able to legally give the firearm back to the owner until all judicial processes have been ceased. The preciding judge makes the call in this instance. Having been a police officer for quite some time I can tell you what usually happens is the firearm is confirmed as evidence and then admitted to the court. The claimant then can ask the judge to release the property. Now, if there is an ongoing trial, especially a felony trial, the judge probably is not going to release your property until it's evidentiary value has been exhausted...i.e., court is over and the appeals processes have been concluded. If the suspect pleads guilty the item will be summarily returned to you as quickly as possible. If the process leads to lengthy court processes and appeals, then it may be a while until the court releases your item...honestly, and you may not like this, but the item is not yours to use as you see fit until it is released by the court. The judge makes this decision and the law provides for WIDE latitude in his descretion. He or she could keep your property as a court required evidence for a LONG time if the process involves a homicide or any other type of first or second degree felonious action.