Thanks again for you suggestions, the addition of a "modified" flag coupled with a regular Save op have been on the todo list for a while now, it can be a tricky task in an app that stores multiple data blocks like this and doing it badly and ie. failing to flag a change in some element would be quite embarrassing. on the other hand I don't want a system that is sloppy and flags change where there is none, ie. blue pixels painted over blue pixels.
I will give it some thought and try and get some solution fitted soon + I'm very sorry to hear you have lost some work.