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.
I'm yet to drive a car with a doorknob but it sounds awesome.