Good point about the rules permitting a team to move the player only one position per match to following match. But I wonder if would be allowed to if the players sat out during one match. Without looking up specifics, didn't one team accomplish that by sitting a player, and then after a skipped match, the player came back moved two places?
Key to the rule is if the player being moved is jumping two players more so than two spots. The rule is not about 'spots' as much as 'players' from each players previous position. Sitting a player does not than cancel out the previous order. If player A was ahead of player B and player C two weeks ago but misses some matches... she can be reinserted at B, but not directly to C. That would legally take another match.
There is also the periodic issue with a player not yet having played during the season but who is better than others. That player can be slotted into any position so long as it is in the order of 'ability.' In your example, when that player missed a match and then came back two lower, was there a 'new' player in the mix that had not previously been part of the ladder that season?
Last match order was X, Y, Z. Coach can, assuming justified on ability and results, switch Y & X. However a new/injured player enters line up for first time in season. He plays NEW player between Y & X. Under rules, X has only switched spots with one player in past line up. Now, the next match, coach could NOT move X back up to ahead of both Y & NEW. Legal, so long as the coach of the line up in question is playing the 'NEW' player in their proper order of ability on the team.
Lastly, you have A, B, C, D. B misses a match for whatever reason (injury, discipline, a day off). When B returns, B must can not be behind D. Despite missing a match, B must be somewhere near A & C excluding the addition of someone completely new other than A, B, C & D.
You can't just jump two players whether you skip a match or not.