Quote: "You said earlier that you'd like to hear a story where it was (A) nice and bright (B) they were wide awake, (C) they weren't high on drugs , (D) they weren't mentally unstable, and they saw a ghost.
Well that story meets your criteria by 75% : He was wide awake (sitting upright in bed, eyes wide open, heart rate beating like a song of DnB. He even crawled back into a corner and the so-called "ghost" was still present when he looked back), he was not high on drugs or anything of the sort, and he is not mentally unstable (I can say that because it occurred only once in his whole life. If he were mentally unstable, he would have had visions and weird dreams multiple times. So what gives? That doesn't make sense)."
I dunno dude. He may have felt wide awake, but he just woke up from sleep in the early hours of the morning. Your heart can be racing and you can still be mostly asleep (but waking up). I've had indigestion before which woke me up at 2am with a racing pulse. In fact, that manifested itself as a dream of me being stabbed because of the pain in my chest! Not nice. Who'd have thought a poorly chewed piece of toast could stab you to death in your sleep?!?
I'll give you an example of a vaguely similar story to your dads. I woke up in the middle of the night once because my girlfriend at the time was getting up to go for a late night weeee

I watched her get up, walk down the side of the bed, then when she reached the bedroom door, she turned and looked at me. I watched her for about 10 seconds as she stared at me, and it started filling me with dread (lol .. people doing creepy things at night isn't good for the nerves!). My heart was racing too. Then I felt something to my left, head snapped left, and there she was lying in bed next to me. When I looked back, the apparition was gone.
Some people would interpret that as some sort of ghost thing. Maybe her spirit walking about? Or someone watching over us as we slept etc. I think it was probably a coat hanging on the door which looked like a person, and I obviously dreamt/imagined her walking away, but it felt really real.
In that same house I also had someone whisper in my ear, as if they were a few inches away. Again this was late at night and I was by myself. I was scared bumming shoeless, and basically went in my room, closed the door and thought "Ok .... we'll forget that ever happened."
My explanation for that? My room was close to the kitchen and bathroom and I'd just brushed my teeth ready for bed, so it was probably water moving in pipes. I can't remember now, but I would've been sleepy (I was going to bed after all), and I reckon a psssshhhhh kinda sound from the toilet cistern filling up sounded way too close in my sleepy daze. That's what I think anyway. But at the time I was convinced someone had whispered in my ear, and I'm sure many people would've continued to believe that.
Oh, turns out the owners husband (we were renting) had died of a heart attack in that house, and she'd moved away and rented it out. His ghost maybe?!? Some may think so.
Anyway, I don't mean to diss your dad at all. I just think at 8 years old, having just woken up in bed, when you're young, easily scared and very open to these things, you may think something is real when really it's not. Now it's so long ago that all he'd have are vague memories of the conclusions he drew at the time. If he hasn't made the decision it was a dream by now, the information is now too old for him to reach a new conclusion. Ya know ... the facts would now be to old and blurry for him to reassess it as an adult and maybe decide it was a dream.
But eh, I hate being a cynical old fool. I wish I did believe in these things, cos then there would be a new frontier to get excited about. Unfortunately though, there always seems to an explanation.