Lost drawn background image

[SimpleSi]

I was experimenting using Pixels blocks for my after-school club and due to getting co-ords mixed up - ended up with a completely black image instead of my hand drawn stars one :(

I then realised that there doesn't seem to be a method of restoring the previously drawn image - I can't reload it as its not a saved image

My workaround is to export any drawn images in future but I'm wondering if a more fail-safe solution could be found as this could be a bit of disaster in class situation

I'm thinking along lines of a cache of previous images