I began to export to PDF, InDesign was urgently closed. I have included it anew, it has restored the document, but for some reason not all. I have noticed it only after three unsuccessful attempts of export. The window with the message took off that background operation is impossible. I began to look through the document from the very beginning and I have seen that several pages of the model in general have disappeared! Or rather, there was a TEXT IN FRAMES, and turns with numbers of pages and were absent.
I don't understand how it could occur. Prompt how to restore everything? And what to make that it hasn't repeated again? If it is necessary, I can provide screenshots.