Keyesen was so immersed in his own world that he didn't notice what was happening in the skies. He didn't see Sylas, he didn't see his Scorpion Lineage's Spirit chained and restricted, and he barely registered that there was a battle.
Maybe to be fair to him, his strength wasn't great enough to see what was happening so far above him, and he likely didn't even bother to remember Sylas' face all that much.
He had heard of Sylas, of course, much like many of the others of the Sanctum had after the fact. But the memories of that day were exceptionally blurry to him because he, quite frankly, hadn't bothered to pay much attention.
All of the other stuff was irrelevant to him. The only thing he cared about was waiting for his own evolution to trigger, for his own time to shine to come.
