Could you provide more details, please? Screenshots, hsreplay.net links, etc?
There is no quest to play 5 wisps. However, there is (in wild only) a quest for Rogue that requires the player to play 5 cards of the same name: The Caverns Below (https://hearthstone.gamepedia.com/The_Caverns_Below). And though wisp is not typically played in those decks I can see howe some people would choose that card.
Are you sure it was not a return to hand? Rogue has several such cards and they are obviously often included in decks that play The Caverns Below.
Having a very lucky opening hand is neither a bug, nor an exploit.
Now if you have reason to believe that your opponent has somehow found a way to consistently get exactly the best opening hand every game, that would indeed be an exploit. In that case, see How to Report Hacks/Exploits/Cheating for how to report this.