Does a Takeout Double Apply to a "Passed" Partner?
If you and your partner are playing standard takeout doubles, this double would certainly be for takeout.  The opponent's have not necessarily finished their bidding yet (the 1H bidder could still bid on), and you have not had a chance to bid before this.  Partner has passed, but you knew that and took that into consideration before you doubled.  Partner needs to trust you, and bid a suit that he has length in, or bid 2NT with the necessary stoppers and strength.  If he wants to pass, he does so at his own peril and should have a hand that can set 2H on his own nearly from the outset.

Given your options, the double is a good bid, and gives you the best chance of finding your best fit as cheaply as as possible.  

One minor point: you really weren't balancing here.  "Balancing" refers to the person who, if they passed, would end the bidding.  Since LHO could have bid over the 2H if they had more strength, you were competing, not balancing.

(Edit: Expanded upon partner's responses)