Wish there was more reason to do this.
One thought that comes to mind is to have the value of the treasure go up the longer it's buried and available on the quest board.
Like for example, a buried villainous skull would get buried, become an unique treasure item and gain a (100 x Days) gold bonus to its base value for each in-game day that passes.
If that was the kinda thing we could expect on the quest board rather than the randomly generated ones I'd personally feel more inclined to go for them...or at least try keep track of them.
That's just my one idea though, what do ye got?
