Looks like a Prius. I have done several head gasket jobs on those. My current daily driver 2010 Prius (commercial use) needed a head gasket at 515k. Now has 670k on it. No oil leaks knock on wood. Definitely nerve-wracking getting everything clean, the FIPG on the cover and then wrangling it in there without disturbing the FIPG.
I am curious. Did you run it before remembering that you missed that spot? I wonder if it would have even leaked. Those two machined surfaces pressed tight together right there at that bolt. Not like it's under pressure or anyting, just splash oil up there. All the critical oil pressure passages are o-ringed. I'm thinking some type of sealing washer underneath that flanged bolt head. Kinda like old Honda valve cover bolts if memory serves. Or just a small version of a drain plug gasket. Those hold oil and don't leak. Or... since it's your personal vehicle, just get it good and clean with brake parts cleaner and fill that entire cavity with FIPG (over the bolt). Just thinking out loud.
Of course this is a moot point now since you fixed it correctly.