have a friend who got locked out once, he cemented a stub of
galavanized pipe into a wall under his porch, hid the key inide the
pipe and screwed on a cap. i seriously doubt anyone would think of
that.

When I lived alone I had a spare key taped to the wiring just inside my
pole light. screwdriver outside, loosened one screw, removed top got
key used that once, neighbor walked up and noted so thats where you
hide your key

I have taped spare car key to wiring harness under car. inconveient but
secure access.