Very sorry to hear. Strangly there is another thread here with similar issues: Unprovoked Factory Reset - #6 by Chris_R.
Even in a “factory reset” the OS stays at the updated version, as far as i know, as only the data partition are formatted. Are the Google Apps still installed? This could help determine if this was a soft or hard reset.
Anyways, as mentioned in the other thread, to recover some of your deleted data (as long as it is not yet overwritten, you can use PhotoRec or TestDisk (same url). You need to connect your phone in USB mode though for that to work.