Unpublished PhD work and unresponsive advisor I finished my PhD two years ago. However, my advisor left academia one year before I defended. I finished my research and successfully defended it (obviously), and have a good draft of my paper, but my advisor is completely inaccessible and has seemingly no interest in it (otherwise he would have answered me or contacted me). Is this work lost forever, meaning I cannot publish it without his consent?
Unless he is truly a co-author and collaborator, beyond supervision, then you can publish it on your own. Advising doesn't automatically imply co-authorship in most fields. If he must be a co-author for ethical reasons, then prepare the paper with him as co-author and send a copy along to him stating that you intend to submit it to "xyzzy" unless you hear any objections. Of course this gives the advisor a sort of veto, but a co-author would have that in any case. 

Within the paper, thank him for his help, as well, I think. Thank him when you send the paper to him as well, of course.