Exhumin' Nature

I just found out about this unmarked quest, and I understand that it wouldn't get any pop ups due to the unmarked nature of it, but is this mentioned at all in game? For instance, to get This machine, you need to complete and unmarked quest where you need to talk to multiple NPCs and follow certain steps to aquire it, same for the Pimp boy being an unmarked quest within another quest, but exists more than just committing an action. I rob those Graves EVERY playthrough and I've never even once been hinted to do so by the game, so how is this an unmarked quest? What actually points the player to do this like other unmarked quests?