In the proposed rules above these are sections that could relate to this conundrum:
6.1 Cue ball fouls only: When a referee is not presiding over the match to call all ball fouls then disturbing a ball is governed by standard "Cue ball fouls only" rules. For clarification, it is always a foul to disturb the cue ball but not a foul to disturb a single object ball as long as there is no effect upon the shot. Any time one or two balls are disturbed, the shooter and opponent must be notified, and the opponent given the option to restore the position or leave the balls as they lie before play resumes. It is a foul for the shooter to restore a disturbed ball without prior permission from the opponent. If two or more balls are disturbed then it is always a foul, whether there is an effect on the shot or not. If multiple (3 or more) balls are accidentally disturbed, they are considered unrestorable and in addition to the standard foul penalty, the opponent has option of ball in hand behind the line.
So since at least two balls were moved it was clearly a foul no matter what. So start there. If it was three or more then we put in place "unrestorable" but added an option of BIH behind the line.
But there is also 6.6 section (quoted below), that offers the possibility of asking an "official" to restore the balls. In this section, it makes no difference how many balls were moved -- the official can be called to "restore" them -- of course to the best of their ability, and the players would have to live with where the official put the balls. Since it would be very unlikely that the official saw it, they would have to consult the players and/or onlookers and do the best they could.
Joe says it was an accident by the shooter. But it's pretty difficult to figure that out, so although this is under the heading 6.6 Intentional Fouls, I would think it applies anyway since it certainly was an illegal technique, whether it could ever be determined it was intentional or not.
Bottom line is, given a day or so to decide lol, I would call it a serious foul, with BIH option, and the option of asking an "official" to restore the balls if the incoming player calls for that -- no matter how many balls may have been moved, and knowing that the restoration would not be perfect -- it is still the right justice for the incoming shooter in that situation if you ask me.
6.6 Intentional fouls: Standard intentional fouls are an accepted part of One Pocket tactics as long as they are played by use of a legal stroke, such as by lightly touching the cue ball with the cue tip; by rolling the cue ball to a new location without regard for legal contact with either an object ball or a cushion; by pocket scratching the cue ball; or by using a legal jump technique to force the cue ball off the table.
However, if the shooter has used an illegal technique, such as pushing, double-hitting or wedging/trapping, to direct or redirect the cue ball or any object balls to a more desirable location such as within the stack or jawed pocket, then the incoming player has the option of either playing the balls where they lie, or requesting the official to restore all such moved balls to their location prior to the illegal maneuver. In addition the incoming player has the option of cue ball in hand behind the line. The offending player is charged the standard one ball foul penalty, and in addition may be further penalized at the discretion of the acting official under the general rules of unsportsmanlike conduct.
Now reading this, I can see as written in our proposed rules, we have a conflict between "unrestorable" in 6.1, and "restorable" by an official in 6.6. So at the very least, we need to clear that up with a "ref" to the other rule or just leave it to one or the other rule.