I have been back, a few times. It hasn't dropped again. No there could not have been another scholar there because only 2 could ever be there at once as the sch is a healer. The second healer was a white Mage and that's not who got the book. Somewhere around lvl 50 summoners and scholars started using diff books
The one I have equipped now is some healing book that my summoner can not equip. It's a sch only book.
My inventory isn't full. I always make sure and I have not gotten any new weapons
I'm at a loss as to how this happened unless it's a bug or glitch of some kind.