If you hold the alt key down, do you get a description for the teleporter stone? If so you can click the description to drag and drop it.
If the problem you had trying to add it to your inventory while overloaded caused the teleporter stone to disappear, or get stuck, you can stick the teleporer stone you have in a barrel somewhere, and get a replacement set of teleporter stones;
Lost Items - guide and directory of inventory filesAlternately, if you are close to finishing the council quests, when you hit the gong to move to the final area of the game your teleporter stones are replaced, anyway (and if they are not in your inventory, the replacements get placed near the start of that area).