So ...
The scenario is to
(1) obtain a 'spare' fob with key ...
(2) 'Hide' the fob, sans key and battery somewhere not that obvious inside the TCH.
(3) 'Hide' the key somewhere exterior and not really obvious, so that in emergency the key can be retrieved to open door and fob (sans battery) can then be retrieved to start TCH ...

Sounds like it would work.

With prior two Camry's I found a place in a wheel well to securely store 'spare' key ... and this little one shouldn't be that hard. Just need to be sure it won't jostle out, or move into a place where it can't be retrieved.