Did this ump stay 1blx because it might be his call if U1 doesn't take it? He was in the right position for the play at the plate but it wasn't 3blx. With balls hit to the infield you don't get much of a choice sometimes.
MLBUM/PBUC allow a RHP to move his pivot foot in the direction of 3B as long as he moves his non pivot foot toward 1B. That is what the pitcher did. They consider this an in contact move. Why would they specify this? If the pivot goes toward 3B and ends up in front of the rubber we know it is not a dissengage. If the pivot foot goes toward 3B and ends up in line with the rubber we know this is not a dissengage. If the pivot foot goes toward 3B and ends up behind the rubber we have MLBUM tellling us to consider this an in contact move.
Need more info. What code? Was the ball batted? If so, was it touched by a fielder or did it go by thru or by or pass a fielder and no other infielder had a play on it? But it sounds like your runner should have been called out due to interference and if the runner was called out properly due to being touched by a batted ball then the ball is dead and runners return?
Did the 1BC get to talk to an ump after he asked? I didn't see the play so I'm guessing the PU had something else to watch: http://bustedcoverage.com/2015/08/27/california-first-baseman-little-league-world-series-cheap-shot-video/
When the ball is not retrievable by the catcher and he is standing or squatting in front of you watching the ball go into the stands they normally should expect to get a new ball from the umpire. But I have no problem if the ump wants to throw it back.
Retired runner is a different rule in itself, 7.09(e) old. If the runner is retired there is no possibility of a batted ball. There is the possibility of interfering with a throw or a fielder making or receiving a throw or any other "play" that might occur. Intent does not matter unless per WUM, you have him running the bases. Then it would need to be intentional.
WUM reference plays regarding old 7.09(e). I didn't upload it but they also protect a retired BR who overruns 1B and gets hit with an throw from a fielder that caught his fly ball in foul territory and is throwing to 3B. That is still continuing to run the bases.
Wendelstedt says this is a retired runner and once they leave the basepath intent does not matter as they are responsible for avoiding a throw. So, in the OP you have to decide if he was still running the bases when he got hit or if he had given up running the bases and was returning to the dugout. Old 7.09(e) protects retired runners running the bases only.
Sidenote: I think Robles is a sideways pitcher. From what I can tell he takes the rubber with his hands together and if he is going to come set he then splits them. If he is going to wind up (his "normal" or his quick one) he leaves them together and proceeds with the pitch.
With open bases, the pitcher is not required by rule to pitch from the set with runners on. It's just a good idea if he wants to hold the runners. If he doesn't want to hold them because they probably are not going to steal or squeeze as with bases loaded or R3, R2 R3 he can and will pitch from the windup. OBR allows a pitcher to stand sideways and windup.