I believe this is a bug that has been reported before. You might want to search the forum here for similar topics. I beleive, though I'm not certain, that at least some users who have reported this found that increaing the size of the empty frame slightly, then moving it back, pulled the text back into it where it belonged.
Check that you don't have Insert Blank Page checked in Book Page Numbering Options.
I'm assuming you're usig the book panel here
lilia, it's unchecked, in fact ID does this even in non-book docs...
peter, moving the text back into its original frame by increasing the size of a newly created blank page may be one of the solution, but nothing better than simply deleting the page. it causes the text pull back, too. what makes me angry is that after this insert ID starts updating of page numbers immediately and when you have tens of docs within a book this renumbering lasts quite long and practically you must stand it twice, because you must then delete the blank page and the renumbering triggers again. i've been angry with this bug since i work in ID... i'm going to check the thread you wrote about. so at least i know it's a bug, not me