In v. 0.8.1 Things were getting tense between me and Tupi. Then all of a sudden my colony disappeared. Then I received an information that I am at war with them (No usual combat box, or an information about them burning my colony) then a message that they agreed to a cease fire. Then another message, that we are at war with each other after all, even thought that mysteriously abducted colony was my first and only settlement and I had no military units to case furter alarm.
PS. And as turned out we were at... peace O_o
You certainly should have received a message that they had burned your colony, and the dual diplomatic messages are annoying. Can you attach a saved game for the turn before your colony was taken? That would make things much easier to debug.
Time to close this one. 0.8.1 is quite old, no save game prevented it ever being reproduced, the attack and stance change code has been overhauled, and testing shows colony burning messages are arriving as expected.