Right so I wasn't on Route 9 but this is almost word for word what happened to me on the A350 coming back from Blandford about two years ago. Left at half 10, should've been a 25 minute drive, pulled into my road at gone 1am with absolutely no memory of the middle bit. Engine was warm, fuel was down, I'd clearly been driving, just... nothing there.
The thing that gets me is I had this weird metallic taste in my mouth when I came round, and my neck ached like I'd been lying flat for hours. My mate thought I'd just fallen asleep at the wheel but you don't lose 90 minutes to a microsleep and arrive home safely do you.
Was there anything in the sky that night on Route 9? Because I saw something low and silent just before my memory cuts out on the A350. Would love to know if the details line up.