My black cat Zippi also had a bald spot under his chin took him to the vet and was tested for mites and fleas test were negative - They also tested for ringworm and that came back negative also. Vet could not explain it- his fur his growing back now.
This is really odd but recently I have noticed that when my 13 month old Zippi (male) gets ready to barf up a hairball he starts walking backwards. At first I thought I was seeing wrong but just the other day in front of company he did it again. Fortunately when he does this and I see it in time...
I have a 1 year old male cat that just loves to scoot. Have had him to the vet and they checked his anal sacs and they were fine -they could find nothing else wrong. Do you think he just like the feel he gets?? Drives me crazy when he does this.