He thanks the WoL to help regain memories, though they are clouded. But the fact he remembered OUR presence in Elpis with such disorientation like it was shown in here -
https://youtu.be/05Dsij325HI?t=338
He mentions the improbability as a lingering trace. There's also the fact even as the heart of Zodiark it's strange his memory was gone yet Hydaelyn's was not?
https://youtu.be/FnaqXPQ3WCU?t=1396 talks about Aetheric blasts that affect memory and of course the convenient plot point later about being returned to the underworld people have memories restored. With Hermes involved with Zodiark's creation...and a memory device that has made one significant appearance...and the fact the Convocation knows about said device. I would not be surprised if it does show up again