Sorry I did not take a pic but,,, I'll try now because it is not fully grown back yet... no my cat did not injure himself,,, no scratching,,, just picking at his hair and licking...

your friends cat may have parasites... I read that cats are very effective at picking and cleaning any visible parasite so you may think they don't have them...
Skink Reviewed by Skink on . My cat and OCD... Well my cat was picking at his back and had a patch of fur gone the size of a freakin grapfruit... Vet said bring him in cause he probably has parasites... I did not bring him in cause he "Buddy" and his brother "Swirly" hang together and Swirly did not have the problem... I researched google and found that some cats have like OCD and clean themselves to the point of removing fur... I took a praise approach and I am happy to say Buddy's patch almost grown back in... What it seems is Buddy Rating: 5