Ok, no actual Transformers appeared in the trailer. It was about a Mars probe that we were told crashed on landing, but the trailer was what had ACTUALLY happened: it landed, it started transmitting, a huge shadow fell over it that was obviously a robot (we could hear it approaching; big heavy footfalls) and then the transmission ended. The tag line was: "It was the only warning we got" or something like that. Then the title and the date.