At least one fatal accident in a Pitts was believed to be caused by the pilot not recognising that it had gone inverted.
I experienced an unusual situation like this (nearly 20 yrs ago now) where I got into an unsual inverted attitude when I was expecting to go into a normal spin.
I tried to abort a stall turn (as I was about to go into a solid cloud base) by trying to kick the Pitts S2A earlier than normal which didn't work as I will still going up vertically in a huge sideslip and then pulled the stick back to make the aircraft just snap into a normal spin to lose height.
To my surprise the aircraft fell on its back in a flat attitude and stayed there which is wasn't what I expected and as I had about 5000ft so I figured it was best to let the aircraft stabilise and then figure out what was going on.
The airspeed started to increase so I figured this was more of an inverted spiral dive than a spin so I tried to roll out of it in a stick neutral position and then the Pitts flipped into a nose down spin. I lost about 3000ft during the whole exercise.
I spoke to a former aerobatic champ (Chris Sperou - Australian Unlimited Champ) about what happened and he said the nose not dropping through and staying flat was symptomatic of not having the power FULLY back it idle , he said even a few hundred rpm off idle can do it with the right combination of factors .
I went out and did inverted spin training after that (with a retired military test pilot) and would highly recommend inverted spin training to anyone flying some of the more capable aerobatic aircraft.