after painting some textures onto my model,
my computer suddenly without reason started to slow down,
so i saved, and rebooted.
when i reopened my file, it seems to not save the texture painting i made (bump maps)
though in the layer tab what i created did appear,
so i right clicked and did “refresh selected” only to get an error like this

is there anything i can do to save those textures?
what caused it, so i can prevent this in the future?
*CTRL+ to enlarge image

