This is similar to a previously asked question, but deals specifically with addressing the problem on the CV. My adviser had a bit of a personal meltdown and left the department while I was finishing analysis of field data/writing up. His students were assigned the following year to a non-tenured professor. This new professor was of little help to me my last year of writing up, sat on my dissertation with no comments for over 6 months and only produced comments after I went to the departmental chair. He did not think much of the type work I was doing and went so far as to say so during my defense. I will add here that I have a number of publications (>5) including single authored ones-which for my field is significant- as well as an excellent track record of funding and in presenting my research. I have a strong CV but have had no success thus far in securing a job. I once saw one of the letters he had written for me (it needed to be included in a single PDF so he had to send it to me) and it was terrible. It talked mostly about him and how he really did not know me well and with a few generic sounding "he will no doubt exceed" sentences that just sounded fake. Months later a colleague suggested that I find a different reference than my adviser (but was not clear as to why).
So, my question is this: since committees will no doubt look at my list of referees and wonder at my lack of an adviser-I have taken to including a short "note" in the "reference contact information" section explaining that 1) my original adviser left academia at the end of my time as a student and 2) that my new adviser was up for tenure the year I defended and very busy and was in a different field than mine, so instead "below are three people who are in a better position to judge me on my research, teaching, writing skills".
Is this providing too much information or is this instead ensuring that rather than questioning and then rejecting my application the committees will stop and think "oh okay, I can see why the applicant did not include their adviser"?
Assuming your field is relatively small, the odds are good that your advisor's fate is known to the community. Unfortunately, such events do happen, for all kinds of reasons—just a few weeks ago I learned that a relatively prominent academic in my field basically had his group wiped out because he was arrested on some rather nasty charges!
While it doesn't seem that your original advisor befell such an awful fate, it is clear that, for whatever reason, he is no longer in academia. However, given that he is probably known to many of the people working in your field, it might still be helpful to try to get a letter from him, even if he's doing something completely different. If you can't, because he has refused to do so, then you are entitled to explain the situation in your CV or cover letter. Be succinct and to the point, and stick to the facts; do not make it into a "sob story," which will not endear you to a hiring committee or postdoc advisor.
And good luck—such situations are always stressful, and are always unfortunate for the students caught up in them. It's one of the pitfalls of academic life, and I don't know of a good way to deal with it.