I'll admit to not being terribly consistent with this, but I imagine if I was it would work nicely. It certainly does the trick when I mention that The Maid is coming though!
Who is The Maid, you ask? Well, let me tell you. She is a fictional third person to transfer the bad guy persona to so Mommy can save face.
She comes in the middle of the night and "cleans" the toys that were left out. Except, instead of cleaning, she just takes them. What she does with them is up to you. I know some Maids who get rid of the toys forever (good will, trash, whatever works) and I know others who allow their children to earn them back with good behavior or keeping their things clean for "X" amount of time. I...uh...I mean "The Maid" at my house is more in favor of the earning things back method. Rewards for good behavior and all that. She just replaces the missing toys in their room in the night when they've earned them.