Losing keys is an ordeal, but thankfully I’m not going through it presently.
What if each set of keys had a unique identifier on it? It turns out, they nearly already do. They keyhole and the teeth of each key provide us with the information we need.
If the average person had a way of cataloging this information, they could get replacements from a locksmith. Perhaps there should be an app which takes pictures of your keys and stores this information for you. There are already methods for reconstructing keys using pictures from afar. I am assuming it would be even easier to get good photos when the photographer and the key owner are the same person.
Reconstructing existing keys may be easier than switching out all of your locks, but since the original keys are still out in the world somewhere, you may need to switch out all of your locks anyway. What if we could get our original keys back?
Perhaps there needs to be a service where you can upload information about a set of keys and your contact information. Then when someone finds your keys, they would upload images of your keys and get your contact information.
In order for someone to know to go to this service, either everyone would need to know about it and use it, or there would need to be a key tag advertising this service, and providing a bar-code identifier for the set of keys. However, a key tag could simply have the phone number or some other contact information, so this service would be unnecessary. Perhaps someone should sell low-quantity key tag printing for contact information.