Board Thread:Skyrim/@comment-114.198.24.211-20150813075902/@comment-6881629-20150813090143

If your on PC check the bugs list for the console commands to skip in the quest forward here, otherwise if you have a save from before you picked up your last gem you could try going back and when you pick it up mash the button as fast as you can apparently it can sometimes make the game think you picked up more than one (i've never got things like that to work though).

The lodge does respawn so you could check back after staying away for over ten in-game days being a quest item though a reset may not affect the gem, check around and under the table too just in case.