Just had this problem and I think I figured it out. It seems when you ungroup, the text/images go back to the layer they were originally in; if you have visibility off on that layer, it will therefore look like they have been deleted.
If you have this problem, check any of your hidden layers; make them visible and see if the group reappears. Once found you can move them back into the layer you had the group in.
ivan
Just had this problem and I think I figured it out. It seems when you ungroup, the text/images go back to the layer they were originally in; if you have visibility off on that layer, it will therefore look like they have been deleted.
If you have this problem, check any of your hidden layers; make them visible and see if the group reappears. Once found you can move them back into the layer you had the group in.
Bit strange!