EDIT: Sorry for rambling on.
Well I was editing a Ghoma (L1) and renamed it something like Ghoma (L2 Floating eye) or close to, increased it's hp, it's misc1, and it's graphic, and next thing I knew it had completely vanished from existance.
Unfortunately, I had no Ghoma 1 enemies set, so I had to save->open 1st->export map, and import map of LV6 (to check lv6 screen boss enemy) to see what enemy was there instead. Well it was Ghoma(L1), it had reverted to default, but at least it was there again.
Where did it go? -I imagine it needed a vacation by a beach somewhere.
Seriously though, it may be a fluke and nothing broke because of it, but a bug is a bug. Although I imagine it's low priority. Maybe see if it pops up again? At least there's a thread for it if this happened to others as well.