This is a bizarre one. :/
So if we rule out Staff/Admin actions, annual wipe & name confusion...
I'd be tempted to say self-deletion, but I looked at the page myself. Doing so is very intentional and requires the input of information.
It's not something that can accidently happen from mis-clicking and lag (and even then, traces of old posts would remain).
I'm thinking it's more likely something like a Staff Mix-Up happened.
But assuming that isn't the case I'm just going to start shooting for the far out/unlikely possibilities until we find a way to track the account.
Is it possible it's another site she joined, not Iwaku?
Is the username up above a typo? Like, maybe what you have us looking for is the proper acronym but the username for the file itself is where the typo lies?