And being the idiot I am, I selected "NAND erase all" and allowed it to finish, smiling stupidly. Surprise, the phone refused to boot up. It wasn't even stuck in the bootloop: it would just start off with the "Samsung" flourish, then the "SAMSUNG" would glow back and forth. I waited for the booting to finish. I gave it ten minutes, an hour, and eventually the whole night; no dice.
I realised my blunder. I took it to a small service center I know, and asked him whether he could fix it. He tried quite hard for a week, and eventually gave up. I took it back from him and decided to take it to a Samsung center. Note, status so far is unchanged. The phone managed to run out of battery waiting for the boot to finish.
Now for the weird twist. While I had it at home today, sitting aside nicely switched off, it magically switched itself on. I was puzzled to see it starting up, but even more bewildered when it started initial setup- as good as new!
So my question: Should I start believing in good gremlins? Or does someone out there "know this feel" and have an explanation?
Looking forward to any theories that would explain this. And if nothing, well... gremlins.
EDIT: I wanted to remove root because I had got myself a Nexus 4 (Yes, yes, I know, quite a big leap) and wanted to pass this on to a cousin. Thought I'd clean up all data and then go about it