The last I heard (even though token ownership through the wallets is how the whole things gets started), ownership is determined by an intelligence. —Either an intelligence associated with the NFT itself, or something bigger connected to SapienMed as a business.
If I understood correctly, you would still be an owner even if the blockchains went down because the overseeing intelligence would still know that you completed the correct procedure to get the NFT. --You would still need to keep track of your own images and audios, but they should still work.
From comments that were made in the past, it sounded like ownership could be transferred even if you lost access to your wallet —transferred by having a physical token and having a well-defined intent to transfer the whole field to someone else.