Vardy, who moved to Leicester from Fleetwood in May, put the icing on the cake after Lloyd Dyer, Ben Marshall and Matty James had given the Foxes a three-goal cushion.
But when he had the ball in the net again near the end, it came back to him off Michael Poke's parry, and City were dumbfounded by the offside flag.
"It should have been 5-0, because Jamie's second goal was onside, and I thought we were very unlucky not to score more goals," said Pearson.
"To score four goals away from home, and create lots of chances as we did, was very pleasing.
"And if our strikers work as hard as they have done tonight, and put themselves into as many goalscoring positions as they did, we will be even more successful in terms of goals this season.
"I am pleased with the overall work-rate and application of the players.
"I am very aware that every game in the Championship is a tough one, but we we play with the same drive and spirit and quality as we did here, we should have a very good season."
Torquay will have £70,000 signing Billy Bodin back from Wales Under-21 duty ahead of a long trip to Vardy's old club Fleetwood this weekend.
And manager Martin Ling admitted the defeat was "a reality check" ahead of their League Two curtain raiser.
"We were well beaten, and we didn't ask Leicester nearly enough questions," said Ling.
"If you're going to play a team of Leicester's quality, you need all 11 playing to their potential. We only had about three doing that tonight.
"We were hoping to pull off a surprise, or at least give Leicester a game, and we didn't do it.
"I thought we lacked pace out wide, that was evident, but we had one or two players missing in those areas, so I could understand that.
"But it wasn't the only reason we lost the game.
"I was hoping we would build on good pre-season performances against Leeds (1-2) and Stoke (1-1), but it didn't happen.
"It was a reality check for us, but we made it too easy for them.
"We didn't cope their movement, and we didn't do enough to test Kasper Schmeichel in any shape or form.
"It might have been a good night for one or two of the players who couldn't play for different reasons - that's how it works out sometimes."