So the teleporter pad is just sending you outside the cave?
Do you have the Silver Breastplate and 4 treasure maps (one of which is called a scroll)? These are also required.
Have you opened all 4 maps? If you have them and the teleporter pad still isn't working properly, maybe the quest status is updated when they are read, or something.
Are you sure you didn't have any rope in your inventory, that may have gotten mixed up with the 4 in that room? I guess if you got rid of the rest of your inventory, you wouldn't have other alcohol, or extra gold hidden under something, etc.
Silver Armour and Treasure MapsIf nothing else works, there are a couple options:
If you are comfortable hex editing you can get into the easter egg area that way. You will need the 4 rope to get around easily, so hopefully they were not part of your problem.
Teleporting Anywhere, via hex editorYou could download the inventory files to get the required items long enough to use the teleporter pad. See the topic below for details, but in this case you would save under a new name, backup your inventory files and replace them with the downloaded ones (search for 'Silver armour upgrade', about 3/4 through the topic below), reload the save, step on the teleporter pad to hopefully get to the easter egg area, save, delete the inventory files and replace them with the backup of the files from your previous save, and reload that new save.
Lost Items - guide and directory of inventory files