Altaria and Dragon Dance

[bullados]

I came up against this in the pre, and I just want to confirm that I was, in fact, right in my ruling.

Altaria's Dragon Dance reads:
"During your next turn, if any of your current Active Pokemon does damage to any Defending Pokemon, that attack does 40 more damage."

I thought that this ment that if Altaria retreated, then the effect is off (in single play). the HJ at my tourney ruled that the effect stayed if Altaria was benched. could you please clarify the ruling for me? thx.