This happened to me some weeks ago, but I only now got around to posting the pictures. I had left my Tough Solar watches out in the enclosed porch in the strong sun, and all of them looked fine except for the AWG-M100B. The LCD's (all three of them) had turned all blank and "positive," but within minutes out of the heat and light, gradually all turned back to normal, one LCD after the other. The moral is: the damage wasn't permanent, but I wouldn't risk it in hot and sunny weather for longer than 10-20 minutes. It might be worth placing the watch in see-through container full of water in such conditions.
All is well that ends well!