Have you called the rental company? I've left a piece of bike gear in a jeep I rented after an MTB trip, they called back and told me I should pick it up if I wanted it.

That said, I love my GPS watch (Garmin Fenix 3). It's harder to see on the bike but works really well for hiking, swimming, running, kayaking, and rock climbing, where my bike computer is less than useful. It's also ready to use much more quickly because it's already on. I get turn-by-turn directions from my watch and use my power meter with it.

The optical sensor in the watch is lackluster though.