I never did any lost claim warranty before so what I say here is all just guessing.
I would think that the “supposedly” lost HAs probably won’t carry the warranty anymore. If somebody wants to claim warranty service on it, they would probably be denied. The mfg may even accept them in at first but when they’re in possession of them, they may confiscate them due to their lost status.
If I were the mfg, I’d even set something up so that when those lost HAs turn up to get reprogrammed, I’d even have some kind of a “black listed” HA list that would render those HAs useless as soon as they get connected to be reprogrammed. Kinda like how cell phone service providers do now by black listing or blocking IMEI for lost/stolen/delinquent cell phones.
Funny, I just saw a pair of Oticon OPN listed on eBay a few days ago for $2500 and it got snatched up real fast. I did ask the Seller about Oticon warranty status on them and never heard back. Next thing I knew it was sold.