I was able to complete the briefcase challenge with only a few hiccups. Initially I was trying to store the reward inside the case but decided instead to spawn the object when you crack the combination. This resolved my problem of the reward dropping through the box colliders.
Similarly, I am using the same button canvas for the cell phone. As you make your way through the game, it will become invaluable. On initial thought, this will be used for communication goals to the player, but I am still somewhat undecided on it's use a this point.