A tip for anyone with behind-the-ear hearing aids.
A friend of mine wears this style. She lost one of the aids while on a long autumn walk. After she noticed that it was missing, she tried retracing her steps, but to no avail. The ~ $2500 aid was gone for good, probably lying under some leaves.
To try to mitigate this situation from reoccurring, after she got the replacement aid, she went to a guy who sells jewelry chain "by the inch". She had him measure the space between her ears (along her hairline in the back). He then cut a piece of thin gold chain (allowing for a little slack) and added a spring clasp on each end.
She put the spring clasp over the "thread" portion (the part that runs into the ear) of each hearing aid, thereby creating a tether holding the hearing aids together. This way if one hearing aid manages to works itself out of her ear, chances are that it will dangle from the chain until she notices.
Her hair is blonde, so the gold chain blends in. For someone with gray hair, a thin silver chain might blend in better.
On the off chance that you happen to notice the chain, it just looks like jewelry.
omni