Player from dugout

[frozenrope22]

Saw this last night. 16-18yr Rec Ball high school rules. Runners on first and third. Batter hits it to deep outfield. Runners are advancing. Ball is being relayed in from outfield. When I look to home plate to see if there might be a play I notice 2 catchers. Not only are the previous base runners giving the up or slide signal but also the catcher from the batting team in full gear including helmet(no he was not the on deck batter). He apparently ran out of the dugout to cheer his teammates. There was no play at the plate and everyone ran back to the dugout. Homeplate umpire didn't notice the extra catcher as he was watching for the play which never happened.

Is there a rule against this or is this just a "don't do that again"?

I can envision lots of arguing if the fielding team had thrown to the wrong catcher but that didn't happen.