I don't know how I did it, but I think I know how.
I set a volcano down and draged the inspector by it.
when I did that I think it clicked on the volcano and the park inspector went missing.
If I do it again I will take pics.

Try to find him in the guest list or the staff list.

The other day I thought I'd try killing the park inspector. On the internet I've seen paths dug underground and the inspector placed there and then sealed in by the would-be murderer. I recalled some of the ways it was possible to get rid of guests in RCT2 so tried one of these ways with the inspector in my park. I also dug a path underground, placed the inspector in it and levelled the ground, sealing the inspector inside. I then deleted the underground path after which the park inspector slowly drifted further underground right off the bottom of my screen.

I chuckled in my throat delighted that he was GONE! But he was back within seconds, standing there above ground on the spot where he had moments before been buried alive.

As much as I would like to believe someone has done him in I agree with AlexWohlbruck – he's somewhere there in your park. He always comes back.

Lol I just tried that and it was hilarious. You'll have to leave the path there for it to work.

Naming a peep "Ghost Town" prevents all peep generation. Including the park inspector.

I was about to do that in my park... then I decided I wouldn't. I guess it stops after you reload the park though.

RCT3 Chronicles: The Dark Inspector Rises

The other day I thought I'd try killing the park inspector. On the internet I've seen paths dug underground and the inspector placed there and then sealed in by the would-be murderer. I recalled some of the ways it was possible to get rid of guests in RCT2 so tried one of these ways with the inspector in my park. I also dug a path underground, placed the inspector in it and levelled the ground, sealing the inspector inside. I then deleted the underground path after which the park inspector slowly drifted further underground right off the bottom of my screen.

I chuckled in my throat delighted that he was GONE! But he was back within seconds, standing there above ground on the spot where he had moments before been buried alive.

As much as I would like to believe someone has done him in I agree with AlexWohlbruck – he's somewhere there in your park. He always comes back.

no.
he did not come back, I looked all around the park and was there for a while.
but I figure I glitched the game.
and yes I looked in the staff list.

.....
no.
he did not come back, I looked all around the park and was there for a while.
but I figure I glitched the game.
and yes I looked in the staff list.

Have you looked through the park after switching everything to invisible except peeps - at ground level, below ground level, and to see if he's in the air somewhere? If he's in the air, after switching everything back to visible you'll be able to tell what he was hiding inside (he might be inside the volcano somewhere). If it's a glitch he might not be upright any more. He might be in another position or he might be incomplete or in more than one location so, if that were my park I'd also consider looking for something that's not an upright shape.

He's not in the air and I deleted the volcano
and I didn't turn anything invisible.