So are you talking about not getting loot to roll on then? I've always seen the chest after digging as well.

Sometimes you'll get a chest's contents divided among the group, with no loot to need/greed. Sometimes you'll get multiple loot rolls from a chest. My most recent was helping a friend with his boar and pieste skin maps, with the best loot received being a NQ silver ingot. Then I do a goatskin map solo and get a blue fox hide AND level 45 aetherial gear from it.

But never once have I got a map and not have a chest at the "X". Only thing I can think of is that you might be digging in the wrong spot.