Hidden interface controls that affect usability

    The other day I was locked out of my car
    the key fob button wouldn't work

    Why didn't I just use my key to get in? 
    First, you need to know there is a hidden key inside the fob.
    Second, because there doesn't appear to be a keyhole on the car door,
    you also have to know that you need to disassemble a portion 
    of the car door handle to expose the keyhole.

Hiding critical car controls is hostile engineering. In this, it doesn't stand out much in the modern car experience.

This also happened to me in a rental. We drove it off the lot to our hotel a half-hour away before we discovered the remote was busted, with all of our possessions locked inside.

I did know that there must be a physical key (unless Tesla?), and the only way I found the keyhole was because a previous renter had scratched the doorknob to shit trying to access the very same keyhole.