Warriors fielded a young side made up of Academy players and guest appearances from local clubs and Hewitt was pleased by the spirit shown throughout.
He said: "We had a very young side out there and conditions did not help us. We were a little naïve in the way we played, but fair play to Plymouth, they were very physical in the contact area and we got bullied a little bit.
"I am disappointed for the lads because if the conditions had been better we would have put a better show on.
"We would have liked to make it four out of four in pre-season. But Richard (Hill) has got to look after the senior player and we have a big game against Bath coming up. It was an opportunity to play the youngsters and give them a go.
"We have to be positive. They will be better for the experience, but it was a big ask to put a group of Academy players with guest players from outside the club against an RFU Championship team."
Hewitt recently joined the Warriors to take on the Academy Manager role and admitted he has enjoyed his new surroundings and getting to work with the young talent on the books at Sixways.
"The Academy still has a huge part to play in this club in years to come. It's about finding the right talent, giving them opportunity and development," said Hewitt.
"The Academy is hugely important and if you look at Harlequins they are the model for most clubs to follow. They have one world class player at the top, some very good internationals and young boys coming through the system.
"I've just come into the job and I am reviewing the whole process. The main focus now is to work with the guys who are in our senior squad, once we have got them in shape we look at what we are doing at all levels.
"It's a rich area of rugby talent here," he added. "It's about identifying the kids young enough, selecting the right ones who are going to come through and focussing on them.
"My biggest thrill would be to see some of these young lads start regularly for the first team. Ben Howard has done well over the summer, that is one player who is putting his foot in the door, and hopefully we can get some others to do that too."