The place is still there. You can search for it from the places page.
https://www.inaturalist.org/places/nat-mountain
I have never tried using an iNat place for submitting observations. I’m not even sure how that would work because places are polygons and observations are points. It looks like things may have recently changed with the uploader though.
https://forum.inaturalist.org/t/unable-to-update-location-with-lat-long-coordinates/47201/3