The WPA ruling on this situation is the following:
"If a foul is not called before the next shot begins, the foul is assumed not to have happened"
My opinion ----- blatant cheating by the player and his team but unfortunately because nobody called foul before he shot the next ball, he/they got away with it. Hope he lost the rack
Hi Peter and everyone else, interesting qustion. Obviously Peter cites the relevant WPA Rule but exactly how that rule would apply in this case depends on some information that hasn't yet been given by the opening poster.
The first thing that strikes me is that most people in this thread seem to have just assumed that when the first player failed to pot the ball which he "thought" he had potted he nevertheless still met the requirements of a legal shot because a ball hit a cushion. Maybe that is what happened but the opening poster didn't actually say so one way or the other, he might have missed by leaving the attempted pot slightly short of the pocket for example, so let's look at both possibilities.
Let's take the one that most have assumed to be the case first....ie that a ball did touch a cushion when he missed the pot that he 'thought' he'd made.
In that case there was actually no foul for anyone to call when he simply failed to pot the ball that he 'thought' he'd potted. The foul doesn't arise until the first player then hit the cue ball towards another ball when playing the next shot that he mistakenly thought he was entitled to. As long as that foul was then claimed by the second player before the first player then played any further shots, the WPA rules would give the second player ball in hand at that time.
Let's now look at the other circumstances which will actually result in the second player having to claim a foul much earlier than in the first scenario......if the first player had failed to pot the ball that he mistakenly 'thought' he'd potted and at the same time had also failed to cause a ball to hit a cushion then there was already a foul before he took the next shot that he mistakenly thought he was entitled to. Therefore in those circumstances the second player would have had to claim a foul before the first player hit the cue ball for the next shot that he thought he was entitled to. He can't wait any longer than that.
Maybe the opening poster can just clarify the exact circumstances of the missed pot that the first player mistakenly 'thought' he had made....ie did any ball hit a cushion?....... and then one of the two above possibile rulings can be eliminated.
Of course if they weren't playing rules which incorporate the same relevant WPA Rule mentioned by Peter then you'd have to consider all the above in the light of the rules that they were actually playing.
Hope this is of some interest and/or use.