I too carry a little 'tool kit'. which I use at least once on every trip, McGyver. While my colleagues are probably right about a magnet glomming on to other metal elevator parts, I'm going to add one to my tool kit - I can see that it may be really useful in many ways. Thanks for posting this.
And bring a magnet or two on your next cruise. Most cabin walls are metal, and you can post papers up there easily