Just get in the habit of checking for your keys before you go through any door. It takes no mental effort once it’s a habit. If they aren’t in your pocket (or in my case a lanyard) then they are in that room or vehicle, so you should recover them before going out. This method worked for me 100% for decades. It only failed after I got married and my wife started stealing them. But it’s usually not too hard to find her.
$ info {command}
although not available for all commands will often give texts that are more tutorial in nature. If you don’t like the interface of info, you can use tkinfo instead.