I am having a very similar problem. I made a PDF from one of my documents (which has a list style set, linked to the heading 1-9 styles), and while the PDF was produced fine, when I returned to the document, the numbers had disappeared. After this happened,
other documents I opened using the same style set ALSO had no numbers. I tried all the suggestions here. I was finally able to get the numbers back by modifying the list style, opening Format - Numbering, and clicking on each of the levels (but making no changes).
When I closed out of those windows, the numbers returned. I did this for each document I had opened and saved them all. But now, sporadically, when I open them, the numbers are gone again. I also sent one of the documents (that had been working last time I
opened it) to a coworker, and the numbers were gone when he opened it. Fixed, saved, closed, opened. Next day - numbers gone again.
I had been using these styles w/o problems for a couple weeks.
Any ideas? I am fresh out of them! Help!