I did not expect that the serial number would come up so quickly
Except the number (or similarity thereof) doesn't mean much, as has been proven in similar situations before. Clinging so hard to this "proof" probably means you have no real proof that this was a Ukrainian missile.
I'm not a prosecutor, why do I even need to prove something? The burden of proof lies with the accusing party, in the event of this provocation, Ukraine falsely accuses Russia of launching a missile strike with a Ukrainian missile from the territory controlled by Ukraine into the territory also controlled by Ukraine. And Ukraine does not bother to provide any evidence!
Such complex products as a rocket consist of many nodes, assembled at the factory on the same numbers, and each internal node has this number, not painted, but stamped in metal (there are at least a dozen of them inside the preserved tail section). And at the Votkinsk Machine-Building Plant, where this particular rocket was made, the archive has paper accounting documents for each copy, including which military unit it was delivered to.