Note: this question contains spoilers for the manga.
We know that Isshin Kurosaki left the Soul Society because he wanted to protect Masaki and help her with the matter of her hollowification. Then they had children, etc., etc.
But before that, Isshin was the captain of the 10th Squad. Rangiku was his lieutenant and Toshirou was the third officer of Squad 10. We also have Rukia, who was in those days already in Squad 13 (if I remember the timeline correctly), so she must have known and been able to recognise the captains.
And then we are back to the main story - Rukia met Isshin and didn't recognize him. And after that, Rangiku, Toshirou, Ikkaku, Yumichika... all of them should immediately have recognized the ex-captain of Sqad 10, am I right? Why didn't any of them recognize Isshin?
Is there an explanation for this, or was this a plot hole created by Tite Kubo? Maybe he hadn't created Isshin's story when he released the Saving Rukia arc and the first Arrancar invasion on Karakura Town arc? Or is there something I missed?