Sounds like a smart cookie to me, blabbing about a possible new job to all the students and his colleagues is only likely to cause him problems, especially if he didn't actually get the new job.
I'm guessing he worked his notice as required and left for the new position as any normal person would do? It would be nice and fluffy of him to stay to the end of term but by then the new job could have gone to someone else.
As above, email him and ask.