Janders has a cloth book featuring an actual (2-in. long) teddy bear going through his bedtime ritual. She calls it "Growl-Growl Bear", because, well, that's what bears do. This one actually sings "Lullaby and Goodnight" if you squeeze it. At least while its batteries were strong enough; now it just sounds like it's being strangled. The book also contains pajamas, a toothbrush, and other things you can interact with.
Anyway...Janders came across her book tonight, but Growl-Growl was not nearby. I took a cursory look around our very messy family room and said we might have better luck if we cleaned up a bit. So Janders went into the cloth book and pulled out the "bar of soap" from the bathtub page. She then went around the first floor of our house and started rubbing the bar on every surface or item she could reach. Yes, she was cleaning up.
Eventually we made our way into the living room. There, on the floor, was Growl-Growl Bear. She saw it before I did. She snatched him up and went right back to the family room where we began playing with the cloth book in earnest.
There you go - anecdotal evidence that cleaning up helps you find things. Tell your kids!