I did what you said, i deleted the local Saved Data. but once i deleted it and started up the game and went back onto my Elf's, the chat window was still missing.
And a new local saved data appeared.
Honestly i don't know what really is going on with it, my Elf's are not playable at the moment.
I could try and see if it will happen on my Human's or Orc's but then again i would not want this problem to happen to them and for them to lose their dragons etc..
So I'm at a complete loss, and I'm starting to see the same problem, just a tiny bit different on what units they lose, with other player's, ever since the new patch.
So i would like to get my units i lost back, but, seeing as this problem of them vanishing hasn't gone away, they might just vanish again if i try, so i will just wait till then, i guess, till this problem goes away, then ill ask for a refund on my units that i lost.
Here is the recent log, if you need it.
And i thought i might just add a screen shot of it, (In picture i do have an army selected near my town).