Is there any reason there couldn't have been both a barrell and a rectangular container?
Maybe the rectangular one contained evidence other than the body...broken nightstand, cleaning items etc. It would be harder to fit a lid on there with pieces of wood sticking up every which way.
I have had several containers like that over the years and when I need the lid I have to hunt around in the garage for the right one...the kids get into them and don't replace the lids or the lid gets cracked or torn when they try to pull it off improperly.
Drew picked an "unreliable" drug abuser for his accomplice on purpose, so he could be discredited on the witness stand if need be. Drew probably either gave him some of the drugs he took that night or gave him the money to buy it, knowing that this guy would get stoned out of his mind as soon as they were done. Heck, DP probably even bought him a bottle of Wild Turkey to wash it down.
Susan