How about this: In the midst of the war for cybertron (before dark energon was used on the core), Shockwave was assigned to travel off world on the Harbenger with to try and retrieve the relics that were jettisoned off world to keep from the claws of the decepticons. Shockwave follows the path that the relics take and winds up on the path to earth, millions of years before the preset day. Once he reaches outside of the earths atmosphere, he gets ambushed by a cloaked autobot ship that had been following him from cybertron (the main purpose of the autobot ship was to take inventory of all the relics and log their coordinates into the iacon database). The Harbenger breaks into two peices and without the knowledge of the Autobot ship, shockwave launches himself from the ship into an escape pod. Little did shockwave know, the falling objects through the earths atmosphere tend to get very hot, so his pod gets sealed shut and warped by the heat beyond the recognition of an escape pod. Shockwave's pod follows the path of a group of relics, and the 2 pieces of the harbenger crash in two different places on earth. Megatron received an automatic transmission if the ship were to crash, so he assumes shockwave is dead. The autobot ship takes note of all the relics on earth and logs them into the database. Shockwave's pod is logged in as a relic as well without the autobot knowing it is really a decepticon escape pod. Unsure of it really being a relic, the autobot scans it and determines it must be since it is a sealed cybertronian pod of some sort. Shockwave, crammed in the pod with no way of getting out, sits there for Millennium, listening to decepticon radio signals and waiting. He is not able to send out any transmissions because that cybertron is too far away. he is able to listen to decepticon radio babble because the harbenger is still activated, and he listens to he story of megatron basically destroying cybertron with dark energon. He grows with rage for he was the one to show megatron the powers of dark energon but he never thought megatron would be foolish enough to use it on his planet, killing it. Since shockwave is loyal to cybertron, he grows a hatred for megatron. After running low on energon, he falls into stasus with his signal cloaked by the pod and the harbenger shuts down. His body lies there inside the pod, waiting for the unknowing cybertronian to cram open the pod to find their treasure, to find him.