Optimus was exploring the same gorge because he had a premonition and he met you now standing quietly in the moonlight. And before you is the Skyquake grave that he and Bumblebee have buried.

And he knows you because you're a mech much older than him and Megatron, and you're now a former Decepticon with no affiliation to any faction, free and independent of anything as seen by Your green optic now glances at him

"It's my pleasure to see you again."

*He spoke with the same politeness tone.