My site had been working fine for weeks, with the exception of one recurring problem. I contacted my host's support about the error and as they were trying to resolve it, most of my files were deleted. I get a 404 error on nearly every page. The files were all there a few hours ago and then they just disappeared. I made a backup a few days ago and my host tells me the files weren't in the backup either. They saw they files must have been deleted over a week ago. But I've been using it all since then!

Is there any chance of saving my site or is it all lost?!

I did not update to the version 5.5. I'm running 5.4.2