@Finnarchist@cybre.space have no other possessions, then it'll be easy to find them.
If you want to try 1. then https://www.thetileapp.com/en-gb/products or https://www.thetrackr.com
Personally I have a small bowl on a table in my living room that I put all my pocket contents into whenever I get home. So either my keys are in my pocket or in that bowl. There's no reason whatsoever to put them anywhere else.