All pages became the same

I have a site that has been up for over a year. I edit it every week or so, usually adding photos. My client asked that I add a page. I added a stacks page, put a text stack and added his copy. I did some minor formatting to the text. Exported the site and using Transmit uploaded to the server.
When I opened the site to check the added page every page had become the same as the page I just added. I went back to the RW file and EVERY page is the added page. I have a backup so this is not as potentially devastating as it could be. But, what just happened?