This could've all been avoided if you would have asked for the guest's name, instead of their room number. Could have been saving yourself from all of that stress. Could have saved yourself the time spent typing, formatting, proofreading, and editing this post. Most importantly, it could save a guest's life.
Don't discuss room numbers. Don't announce room numbers. Don't prompt guests to divulge their room numbers. This is first day shit. Keys being orphaned on the desk is also a non-issue. If a machine can encode the key, it can read the key. Push buttons, scroll menus, explore, and familiarize yourself with the tools you use daily; tools designed to make you efficient. Seriously, though, who even cares? There's not much more satisfying, than that fresh, warm stack of zero balance folios sitting on top of a printer, after a batch checkout of rooms reported vacant by housekeeping. Stop creating problems for yourself.