User blog comment:Godisme/Everything But The Rain Op. 3 Dark of the Moon/@comment-6603670-20130319033747/@comment-1393830-20130319035259

Rukia seems to be the only one who has seen Isshin, he avoided the others. As for why Rukia did not recognize him, i'd chalk it up to two things. 1. At this time, she was a lowly unseated officer who likely did not know all the captains very well and 2. Isshin has definitely aged. You can see his face looks more worn and he doesn't look quite so young as he did so if she had seen him before, he likely is not recognizable to her due to having aged.