Vern’s Volvo is the one he’s been driving for twenty years, not the heap of parts. Even if Grace recreated the Volvo exactly, it would still not be Vern’s Volvo.
The word “Vern’s” infers ownership. When one owns a car, he takes care of it, pays the bills, and assumes responsibility for all the parts inside it.
The original Volvo, before any parts were replaced, was Vern’s. However, as soon as he picked up the car from the shop with the new part(s) in it, he once again assumed ownership of the car, but this time his car included the new part(s). This happened each subsequent time until his car was not made up of any of the original parts.
As soon as one of the original parts did not physically make up the Volvo Vern was driving, it lost all ownership connection with him. For example, let’s say that Vern collected trading cards. Once he traded a card in exchange for another, what was once his card was now another’s. Just because the card was once Vern’s does not mean that it continues to be Vern’s after it is knowingly and willingly traded.
Additionally, even if Vern thought he retained some ownership of those parts after they were removed from his car, he believed them to be destroyed or otherwise used in other cars. His perception was that there was no way for the part to be reincorporated into the Volvo he was driving. This would reinforce even more the fact that the parts did not belong to his Volvo.
As a counterargument, one might present the idea that Vern’s emotional attachment to the Volvo made of the original parts makes it his Volvo. However, take for example a house. Mr. and Mrs. White sell their first house to Mr. and Mrs. Green. Mr. and Mrs. White have a huge emotional attachment to the house because it was, for example, where their child took his first steps. However, as soon as the deed is in the name of Mr. and Mrs. Green, the Whites can no longer call the house theirs. In the same way, no matter how much Vern loved his car, as soon as he pays for Grace to remove and replace the parts, they no longer belong to him.
If Grace decided to recreate the Volvo, it would not be Vern’s. As previously discussed, Vern lost all ownership to the previous parts as soon as he took responsibility for the new parts. Vern would have no more ownership of Grace’s Volvo than he would have ownership over one of the thousands of identical-looking cars Volvo makes in a year.
Vern’s Volvo is constantly changing, just as many things do in the world. As soon as a part in changed or a bug hits the windshield, the definition of what Vern’s Volvo is must mutate slightly to include the change. However, as soon as the definition is narrowed, Vern’s Volvo of the past is no longer Vern’s Volvo of the present.