The group found phones, credit cards and earrings, all of which had been handed in to Mission Estate, if anyone is missing items.
The college uses the clean-up as a fundraiser - this year it will help send the Under-15 and 1st XV rugby teams to Chile over Easter.
Melloy said they did not know how much they had raised this year, but imagined it would be around $10,000.
A couple of people took to Facebook to complain about the state the Mission was left in after the show.
One of them, Claire MacGregor said as a country we complain about tourists littering, and it's probably time we looked at ourselves.
"Not good enough people, from food and rubbish to chairs, blankets and goodness knows what else. Not only is it disgusting - think of all this on our environment."
"I'm totally in for a good night, but no need to be lazy and disrespectful."
Others pointed out there could have been more rubbish bins to help people dispose of their rubbish.
"They needed many more bins. All the ones I saw were overflowing. I think we NZers are pretty good generally at putting our rubbish in," Denise McBride said.
Promoter Rob Jefferson said overall the concert had been great.
"The audience seemed thrilled with having Phil Collins right on stage in front of them.
"Everyone seemed to be singing or mouthing the words."
He said Collins was one of the world's biggest, and most popular artists of the last 50 years.
"The crowd seemed to reflect this in what felt like a very warm atmosphere on a night a few degrees cooler than the day before."
Police said there were no arrests made at the concert.
Mission Estate did not immediately respond to requests for comment.