Second the PP who recommended Tiles. They are great!
When my keys go missing, it is usually because I didn't need to use them to open the door when I got home - for example because DH was already there, or because he met me somewhere and we we went home together. In that case, they are usually tucked into whatever bag or coat I was wearing.
And if it isn't that, I put them down on a random worksurface intending to put them back in the drawer but didn't, and mine would be as hopelessly lost as yours if I didn't have a tile attached to them on account of knowing how rubbish I am keeping track of stuff like this!