I so didn't know you had to clean it a certain way. I was sitting there for a long time trying to scrub what I thought was...I don't know what I thought it was. At first I thought one of my cats or my rat had walked over and left a present that had been hidden all this time, then I thought I might've dropped some food or something and forgotten about it. The area was in a spot where you'd have to be really looking to find it. Beside my rat's cage stand.