I just had a game where the ball stopped on the top of the left slingshot.
I didn't attempt a sideways nudge as I was confident that would dislodge it (although maybe not, judging by the discussion I've now seen in https://www.pro-pinball.com/forum/viewtopic.php?f=12&t=215&start=10#p1026), but I was curious to find out what would happen with a vertical nudge.
Slightly to my surprise I found that while a vertical nudge pushed the ball up, it just settled back on the same spot. Clearly the physics of the situation allowed for no sideways motion whatsoever.
I then decided to find out what happened if I triggered a tilt with repeated vertical nudges. Naturally the game's attempts to retrieve the ball after the tilt all failed. That was my last ball, and so the game then asked if I wanted to continue -- and the stuck ball vanished from the table.
Just to be certain I continued the game, but the ball was definitely gone.
I can imagine reasons why this might have been done on purpose, but it rather spoiled the illusion of it being a real table. It would have been great if the ball at least remained on the table until a definitive decision to end the game was made (and ever better if it was still there for the next game, had I decided not to continue).
Instead of experiencing a very cool rare occurrence giving me a chance to get an old ball back in play and making the table seem that much more real, I was instead a bit disappointed at the game's failure to persist with the simulation.