Hales had been due to play for Nottinghamshire against Durham at Grantham having served the drugs ban that ended his World Cup hopes.
But the game was washed out which meant that Durham could not gain the win that would have prevented Yorkshire from reaching the knockout stage.
As it is, Yorkshire could yet qualify if they win their final two group games against Worcestershire at New Road today and against Durham at Emerald Headingley on Monday - provided that Worcestershire do not win at Derbyshire on Monday to boot.
The permutations are predictably complicated, with sixth-placed Yorkshire still having much to do to make the top-three, with the winners of the North and South groups going straight through to a home semi-final and the second and third-placed teams from each group facing each other in quarter-final play-offs.
With most wins the first tie-breaker for sides finishing level on points in the groups, Yorkshire have won fewer matches (two) than all of their rivals for a knockout berth, with two of their six games finishing as ties.
Throw in a one-run defeat to Lancashire as well, and the overriding feeling for Yorkshire is one of frustration that they have not secured up to three more wins.
“The cricket we’ve played, we feel we should have won four or five games,” said captain Steve Patterson.
“Winning the first game against Leicestershire so comfortably, by over 200 runs, was a fantastic start to the tournament.
“Then we’ve stuttered from there with the two ties and also the loss to Lancashire.
“We were beaten fair and square in our match against Notts, and you can accept that because we didn’t play well enough on the day. It’s those close games where, at one stage in all of them we were in control and didn’t see it through, which causes frustration.
“To get a win at Northants in our last match was fantastic for the lads, and we’ll take that into the Worcester game and see how we go. Worcester are a good side, we know that, but if we play to our capabilities we’re confident we’ll win the game.”
Yorkshire have made one change to their squad from that match, batsman Will Fraine having been released to play club cricket this weekend.
Yorkshire (from): Ballance, Bresnan, Brook, Coad, Kohler-Cadmore, Leaning, Lyth, Olivier, Patterson (captain), Pillans, Poysden, Tattersall, Waite.