Not a bug

The hidden achievements are visible in the global achievements list on Steam

wrongwayjerry 3 years ago updated by Tyler Owen (Lead Developer) 3 years ago 4

FYI - when looking at my personal achievements it says I have 3 hidden left to discover. However, if you look at the global achievements list it shows all available achievements including those that are marked hidden in my personal achievements. Not that it helps much since i need to discover 3 locations and i don't know where they are. :-) On a side note - one of the hidden achievements is to discover a "drill rover" which i thought i had done already. 

That's how Steam works in terms of "hidden" achievements; they're only really hidden (at least globally, they are still hidden on your personal list) for as long as not a single player has managed to earn them. There's nothing a game developer can do about it.

As for the Drill Rover, did you find, by any chance, a bugged location for it? Currently there appears to be a good version of the site which gets discovered when you approach it (and thus awards the achievement) and a bad version that doesn't get added to the map and as a result doesn't trigger the achievement either.

I found "Drill Rover Storage" at 283.072 -6.4689 - don't know if that is the bugged location or not.

Yep, that's one of them. So it's consistently bugged at a specific location, which is great since it narrows the issue down to the location itself, not the site (which can appear at various locations randomly, I think), so might be easier to figure out what's causing it.

For reference (and possibly to report other locations): https://lacunapassage.userecho.com/topics/228-drill-rover-site-not-added-to-map/

Not a bug

I'm marking this as not a bug since the primary post topic is just how Steam operates. Others can follow the link Mr. Fusion posted to see progress on the location discovery bug fix.