No, I didn't change themes. I have changed themes since owning the 8100, but that did not effect my call log or messages, at that time. Honestly, I did nothing that would have prompted this deletion. Keypad's been locked and the phone was in my pocket. I just went to call a number and noticed all previous calls weren't there, then I checked around and saw all the messages I received after 12/12 weren't there either. odd.