The 'miss' rule can be suspended at the referee's discretion. It happened at 14-10 in the Carter v. Maguire match. The snooker needed a three-cushion escape, and Carter tried it four or five times, but was called for a miss each time. Then he tried again and missed by such a tiny gap that the referee just made it a simple foul stroke. It was up to Maguire whether to play from there, or tell Carter to play from there, but not to have the balls replaced again.
If the snooker just looked impossible via no matter how many cushions or how much spin, the player would have to make a plausible effort, and if the referee decided it was the best effort that could be expected, he'd give the foul, and the other player the choice of who would play next from wherever the balls had ended up.