Today, I found my Samsung P2's memory wiped. Completely gone, no games,

[Platinum_G]

music, pics etc. what happened? it was perfectly fine in the morning, and it was charged, but i hooked it up to the computer to charge again anyway. 8 hours later, when i got back from school, the memory was wiped, and it had no files recorded, nothing. Not even the pictures that are default, and the games that come with it. Why did this happen, and what can i do to make it go back to normal?