We might also investigate the transit logs on Onwia Guard. We already have a backdoor in their systems from back when we made sure they didn’t notice us entering and leaving Onwia, and their gate is the only way in or out of the system.
It might not tell us directly whether the Hegemony found our base, but we could look for suspicious activity. And at the very least it might tell us which Hegemony ships were active in Onwia and may have discovered us. With that information, we could determine where to look next.