I had the same exact problem with a black Pages logo appearing instead of all of my documents. What I did was delete Pages from my iPad and then reinstall it. After it finished I restarted my iPad and opened Pages. Maybe 10 seconds later all of my documents started popping up and began downloading from my iCloud. And now they're all there again! Hope this helps you. Give it a try.
In my case, Apple really messed me up. It turned out that the iPad trashed all of my documents and the only documents it restored was a document I created after I discovered the problem, and a copy I made of one of the trashed documents, which only shows the icon and can't be opened. Obviously my iCloud is working because it saved those 2 documents, which means with the iPad trashed my documents it also wiped them off of iCloud. Going to be very hard to every trust Pages and iCloud again. Thanks for the help.