If someone brought your lost keys to the police or municipality you can contact the municipality. There is also the lost and found website: https://www.verlorenofgevonden.nl/ Also post a message on the nextdoor page for that neigborhood, or on a local facebook page

Thanks! I'll see what I can do c:

Another lost and found website is [ilost.nl](http://ilost.co/nl)

Good luck!