That's a good question. I was wondering that myself. But in one story, when Gigantic Dark told Guyver US how Guyver units 1, 2, and 3 were found, Guyver US wondered how his unit was found. In the Time War, the Zoalord that remove the Guyver Zoalords unit was sealed within a cave when he was Megasmashed. Could Guyver US's unit be the discovered Guyver Zoalord's missing unit?