While you're waiting to find a locater device, order a bunch of those
dog-tag things they sell at the vet with your name, phone, address on
them. Hook them to your bridle and saddle and halter, whatever. That
way, if your horse gets away, people know where he belongs. An animal
control person gave me this advice once saying that it's surprising how
many horses they find wandering around riderless and they don't know who
they should contact.