Common problem.

I usually request two. One I keep in the car. One I keep in my back pocket (I'm a women so my wallet is in my bag).

The above is usually sufficient. But I did once have a door lock completely die on me. The front desk couldn't reprogram it when their little machine. I ended up waiting in the lobby for an hour while they called a maintainable guy back in from home. He already had to take off the lock. Another time the hotel's entire lock system was malfunctioning. Apparently it didn't know the real time. So one employee had to go plug in to every door lock to reprogram them.