Wow, that's terrible. Google's systems probably recorded the IP address from which the account was accessed, but I don't know what you need to do to get access to that information. The data copied by Sync probably does not include IP addresses used by the other devices on the account. Mozilla's web logs might include that information, but I don't think it would be readily accessible. You might need to speak with someone in the legal department. I suggest phoning the Mountain View office 650-903-0800 to see what would be required to release that information.