“It was a bit of a shock really. I thought I'd done enough,” Stone told Mark Plumb in a Mansfield Town News & Views interview.
“I thought given my age and first real season playing I thought I had played well in enough games and had got us a point or three points in some games and kept us in it.
“I thought I had done enough to earn a new contract. But that's football.
“I understand where the gaffer is coming from. You have to move on and prepare for your next challenge.
“It was quite a good conversation considering the outcome. He said my experiences will stand me in good stead for the future.
“I have had a couple of offers come through, so it's just a case of finalising personal terms. I am just keeping myself fit and ready.”
Stone said he will look back on his time with Stags fondly.
“I think it was a successful time as I went from playing U23s football and not thinking I was going to play League Two or One for numerous years,” he said.
“To then having played the good amount of games I have played, it was progressive and I have learned a lot over two years.
“I will be the first to admit I made a few mistakes. That's going to happen – I am 21 and it was probably my first real season I played consecutive games in.
“The gaffer said it was all part of my learning curve and how I will get better as a player. It's not always about pulling off the big saves as you know you will always do that.
“It's how you react to your mistakes and what you do the following game. To start the next game made you realise he trusted and believed in you.”
He added: “I'd like to say a massive thank you and goodbye to the fans.
“Since I walked though the door they have been very welcoming and positive towards me on and off the pitch. That's something I tried to give back as I used to be in that position.”