Dragon Age 2 - Stuck in Wayward Son Quest

I recently started Dragon Age 2 - I'm about twelve hours in and ready to hit the Deep Roads - but before I can do that, I need to finish up any outstanding quests. The only main quest that I haven't finished is the Wayward Son quest, but I cannot move forward in it because it's glitching. I've killed the slavers in the warehouse at the docks, but the next objective is through a locked door. I think the key is supposed to be on one of the bodies, but I didn't get it when I looted them. After leaving the warehouse and then coming  back in, I found one body lying on the ground that was sparkling, which indicates that it can be looted, but the game will not let me click on it.

I've scoured the internet for solutions, and people have supplied several involving enabling the console, but I'm playing on Xbox 360, not PC, and as far as I know you can't access the console when you're playing on an Xbox. I've seen people suggesting that I reload the previous save, but I broke this quest fairly early in my playthrough and - not realizing I'd need to complete it to move forward - I continued playing and put it out of my mind. The only save I have prior to this glitch is only an hour and a half from the start of the game, meaning I'd essentially have to start the game over. If at all possible, I would really, really like to avoid that.

This is a major game-breaking bug, since I can't move forward without finishing this quest, and I know I'm not the first person that this has happened to. Is there any fix for it?