My Kindle occasionally wedges ... it ignores my Next Page press, and in 60 seconds or so, it will dump me back to the index. I don't have to do any resetting, it eventually comes to its senses, but it is back in the index. I've discovered that when the Next Page is ignored (and I pressed it again to make sure I really pressed it) I should make a note of the "number" listed at the bottom left. When it dumps me back to the index, it usually has forgotten what page I was on, and entering the book again puts me quite a number of pages further back. So I just select "Goto Location" from the menu, type in the number I took note of during the freeze, and voila! I'm all set.
So -- I do use those number occasionally! (Though a page number would work too, in this case.)