i think all that picture tells us right their is the owner left a problem way to long
something like that would take 3 days min to happen
from the 1st signs of a problem i would have removed the FF
how chould that have happened without the owner seeing something was wrong
when my FF started sucking on my female to much i took it out and put it in a 2ft tank you would be mad to let it go that far without doing something
dont forget the owner is saying the FF was only 3inch even a 12inch FF wouldnt be able to do that much damage over night
as soon as my FF touched my ray it would swim off
below is a picture of what my FF done in 2 weeks it wasnt bad enought to remove the FF