I logged on to WordPress just to check what plugins I had installed to make sure I had them on my other sites as well. But when I clicked "Installed Plugins" I got error messages all up and down the page something along the lines of "Plugin doesn't have valid header" and when I refreshed all the plugins were gone.
Why has it done this and how can I restore them all? Most of the plugins had data in them such as testimonials that I want to get back. Also I had a backup plugin installed.