I just feel the wording of the card is a little funny. There is no need for the word "back" as if the card said "You may add a burden to take this card into hand," it would still make sense (and then I'd have to agree that this ability could be used with
Dammed Gate Stream). However, we have that annoying word "back." I guess this is going to have to go by popular opinion, as it is a linguistic subtlety, not anything in the rules (unless someone knows about about some clarification made by Decipher!).
When Gandalf said to the Balrog '"Go back to the shadows from whence you came!"' suppose that the Balrog had never been in the shadows. It'd have been perfectly in its right to point out to Gandalf that it couldn't do it, humiliating its opponent and probably putting Gandalf totally off guard before their fight.