i accidentally got my bb wiped when i let my little nephew play with it, and it did a wipe... i wasn't concerned since i had recently backed it up... but the thing was that it didn't get any "error" and a white screen, the blackberry seems to have rebooted itself, and started off fresh just like as if you were to have gotten a new phone
I guess that your nephew activated the right sequence...At least you backed-up your data
thats pretty crazy too...cause the "right sequence" is typing 'blackberry' to confirm a security wipe.
if he was old enough to know how to type blackberry when prompted, then he probably knew he was about to wipe the device heh.