It's easy to hide the backpack in the ruins. I hope it won't be hard to pick it up, if the bandits don't get in the way.PDA message
The backpack is on a ledge at the south end of the east wall. Start from the north and go up the large cement slab, jump to the ledge on the left and follow the ledge around to the south end. Go through the window opening and drop down on the ledge to get the loot. You can just walk off the ledge to the ground without taking too much damage.