Samsung Galaxy S4 — Strangest thing I've seen yet...GF's S4 rebooted to factory settings today

Long story short, she's ready to fling it out the window and go back to the dreaded crApple... She states that the phone was sitting untouched on her desk when it rebooted, and came back up as a brand new phone...all apps, contacts, appointments, everything's gone.

The odd thing is that she didn't mention having to sign back into her Google account as you normally do with a new phone (was hoping we could sync her stuff back in that way of course). Unfortunately she's out of town at the present, so I have no way of getting to the phone to take a look at it myself. I told her to see if she has access to the Play Store and if she has Google listed in her settings/accounts section, but other than resetting it again to see if she gets the Google login I'm at a complete loss. I have yet to find even one instance online where anyone had a similar issue. The phone is not rooted, reromed, or anything of that nature (she wouldn't let me...lol), and it's not a hijack where she's getting a message to pay to get her info back...I'm completely in the dark (short of some kind of major hardware issue), so I was wondering if any of you good people had any thoughts on it? Thanks!