This has happened to me more than once. I create different versions of a multi paged layout using "Create Alternative Layouts" in the pages panel. (for example pages 1-5 is one version of a design and pages 6-10 are a different version) When I close inDesign and reopen the next time, the layouts (which DID exist side by side and separately in the pages panel) are LOST and the pages all run together, separated by a triangle "section" marker instead..
can anyone explain this or has anyone had this happen? have a fix?
From the Pages panel menu, try View Pages > By Alternate Layout
Steve is right on that...I find this behavior strange, though...when I change the Page view (either with no document open or with one open), that view holds for every document I open. New ones or old ones. It would make more sense if the view "held" to whatever I chose last. If I'm working in Alt Layout view in one doc, then work in another that I need to view vertically, when I switch back to that first doc, I'd still like to see the alternate layout view. Annoying.
That was my very long-winded and complain-y way of saying, "It's a pain. Steve is right, switch the view."