Tuff Fluff

I originally saw this as a picture book, but it's been redone as an early chapter book. Set in Los Attic, meet Tuff Fluff, private investigator, who is about to be visited by an enormous, blue bear and a yellow, stuffed duck. Ducky has stopped talking and now only quacks. The troop heads to Ducky's house to get to the bottom of this. After interrogating the beanbags, AH HA. Ducky's brain is missing. Who's got it?