I have the same problem. Hundreds of notes are missing on my iPad, and lately, on my iPhone also. They are available on my other platforms (Windows, Mac, web). Today I removed the Evernote app from the iPad, restarted the device, power cycled the device, and re-installed over cable from iTunes on Mac. It didn't help. I wonder if anything can be read out from the activity log, which I have sent to Evernote support on a few occasions. Its exported immediately after this re-install procedure. The activity log is attached. Or at least I tried to.