The law on this is going to vary from State to State, and I cannot offer an opinion as to your State’s laws (especially since I don’t even know what State you are in), but assuming that you are in the United States, I would be very surprised if you didn’t have laws covering a bailment, which is the legal turn for turning something over to someone else to do something with it with the expectation that it will be returned. A dry cleaner is a classic example of a bailment. If you have any paperwork from when you dropped off the hearing aid, now would be a good time to read the fine print, just in case the agreement modifies the standing law. So, first of all, I would be very surprised if an established practice didn’t make an effort to make this right, but the real question is what the heck happened – it didn’t just vanish? Second, a suggestion that they discuss it with counsel before making a final decision might not be amiss if they do try to tell you that you are out of luck. Third, you are probably within the jurisdictional limit for a small claims action. I would be very surprised if this isn’t resolved favorably and without the use of the legal system.