Sky Seal Stone Broken again?

I was playing against a Miraidon deck. I was down to 4 prizes they were down to 1. I hit their Regileki vmax and left it with 10hp, they of course retreated it and I bossed. I then used sky seal stone using my zacian and KOd the regileki and only got 3 prizes. the stadium in play was temple of sinnoh. They then came in and hit my Gardevoir EX for the KO and won. A game I had beaten but the vstar power simply didnt work!