Lizard, put a big something onto the key, so you can't miss it.
At home, my kids (and missus) were always losing the keys to the back of the house.
I got a piece of 5 ply, cut it to 6" x 4", painted it in fluorescent orange, and attached it to the keys with some wire.
Keys did not go missing again after I did that.
On a similar note, we have a ute at work that is available for everyone to use (it lives at work, it doesn't "belong" to anyone).
The storeman was always going home with the keys in his pocket as he used it the most, maintenance dept got sick of it so they made up a ring out of thick stainless wire about 5" in diameter.
Yeah try and that in your pocket
Keys never went to his house ever again.
Cheers M