Interesting thing I just noticed: I just created my 4th unique Item from a sage (3rd this month). Now, the sage needed only two items, of which I have a plentiful supply. Unfortunately, in the next hour after the creation he had disappeared. What is odd about this is that another time when I created a unique Item from a sage, and only had enough items for one Item, he was still there the next hour.
I wonder if there is any link? What was it that made the sage disappear the one time and remain the first time? Thoughts/ideas/theories?