I have been locked out of the house multiple times after a lock change that reversed how the knob worked. So we finally got a spare key and did what anyone would do test it first before hiding it.

Come next time i got locked out to my surprise the spare key did not work.....No Idea why no idea how but now I cant rely on a spare key incase of being locked out. A small locked out prep kit is what I came up with and if you can afford it throw a pay as you go phone cheap as you can find in there.