He’s gone to an organic planet.
Starscream tells him first. The fragger offed and ditched Cybertron on a golden ‘Ark’ – as the shrieking coward calls it – taking the majority of his fleets and spreading them between the cosmos. “Beyond our immediate reach,” Starscream chuckles beneath his increasing rage, wings jittering. “And past your favourable DJD’s grasp. The message,” and there’s a comm link, trapped beneath encryptions, familiar and brash and so much like Prime’s style, “Says to join him, uh, here, my liege. It’s for his troops.”
“Can you track it?” He growls, and Starscream cowers.
In the end they can. And they do, and it comes to this; the blasted glitch went to a fraggin’ organic planet, calling all troops to his position to rally for the Allspark.
Megatron swears and, shoving aside a rambling Starscream, bellows for Soundwave.
He needs Nemesis.
"I am Optimus Prime, and I leave this message to my Autobots; I have found the Allspark. Join me.”