Sign of the Ancients can be obtained for completing quests in Beorn.
Once you load it to your Sled, you must manually unload it by clicking on your Sled, going through the equipment and clicking the 'UNLOAD' button.
When you go to Storm Canyon, you must manually unload the Sign of the Ancients. It will NOT automatically be added to the location storage.
Once you complete the quest "The Second Attempt" in Storm Canyon and apply the Sign of the Ancients, you will NOT get it back and no longer need it.