Oh dear! I don't know. Does it look sore i.e. red? Is it swollen, or anything untoward other than simply a bald patch? Does it look irritated? Does the rabbit "favour" this area, as in does he/she scratch it or lick it a lot? Have you had a look with a magnifying glass to see if you can see little white flecks which could be mites?
If the answer to any of the above is "yes" then you need a vet to check it over.
If the answer is no, then I don't know. What I would suggest though is if your bunny likes the sun, the bald area is now susceptible to sunburn so be very, very careful. Do not, however, apply human suncream as this could very well be toxic to rabbits.
Give it another few weeks and if there is no sign of the fur growing back, then maybe pop and see your vet for a check-up, make sure the fur follicles/roots haven't been damaged by you pulling it out. Fur should really grow back unless the roots have been damaged beyond repair. Did you see blood when the fur came away? If you did, then the damage could very well be permanent and you may have to change your method of combing them as it seems you may be being a little heavy-handed (sorry, no offence meant) if it always happens - but only if there was blood.
That said, if the fur is ready to come out, it will - I gently pluck our rabbits and plucked a small bald patch on Coco's shoulder last year; I was horrified :lol:! However, it grew back within about 6 weeks. But it was obviously ready to come away and she never batted an eyelid as I was doing it.
It could be that Bobby's fur is taking a little longer to come back, might be age related? I have no idea, I'm just guessing
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