Matson, who scored 28 goals last season, signed a league registration form with the Daniels but has turned down a contract offer and returns to Outgang Road.
But Keast criticised Matson saying the striker has not contacted him with the news.
He said: "I've been told about this but the player himself hasn't picked up the phone – I haven't heard a word from him.
"He made the call at the end of last season to say he really wanted to join us - I did not go on a chase for him. I met with him and decided to sign him and now I'm being told this.
"This isn't the first time either. Last season I was told the player wanted to sign and then it never transpired
"I have to say it's typical of dealing with these people and I'm in no way surprised it's been conducted in this manner."
Matson, who was also linked with a moved to Boston United last season, said he changed his mind because of the ambition shown by Rangers boss Tuncay Korkmaz.
He said: "Deeping have made it clear they want to get promoted this season and continue to improve.
"Tuncay is an excellent manager and has done a lot of positive things this summer.
"The club is like a family and it would be a shame to leave when we seem on the verge of doing something special.
"I'm now focused on helping the club progress."
Korkmaz said the decision had been Matson's alone and that he had been planning for life without him.
He said: "From our point of view Danny was leaving and I did nothing to try and change that as he wants to play at a higher level. He still wants that but believes he has a better chance of achieveing his aims with us.
"Of course it's a big boost for us but I had already signed Ashley Stevens from Blackstones who is an excellent striker and I have some other players training with us. Danny's return means the squad will have even more quality and I'm very confident we will be challenging for the top three."
Korkmaz said he would never have closed the door on Matson and believes the striker felt he owed the fans and staff at Deeping.
"He knows this club and the players and he knew what we were building here and wanted to be part of it and show his thanks to the fans and everyone involved."
Matson praised Stamford but said he believed Rangers to be the area's most professional club.
He added: "Stamford are a good club with decent history and are putting together a reasonable side.
"I have a lot of respect for Keast too, he's a great boss.
"But for me, Deeping is the place to be – the club is moving forward on and off the pitch."
Keast did receive a boost ahead of the Daniels return to pre-season training last night with exciting winger Tyrone Kirk agreeing to stay at the club.
Keast said: "He's a very good talent and I am looking forward to working with him.
"I have two or three more who will be training and I'm very happy with how we're shaping up."
Meanwhile Deeping have lost 17-goal midfielder Michael Stevenson due to work commitments.
Stevenson, who was part of the Rangers side that won the Eagle Bitter UCL Premier Division in 2007, has joined Holwell Sports.
l The Daniels have announced an additional pre-season friendly.
They will host Soham Town Rangers at the Vic Couzens Stadium on Thursday, August 7.
l The club is holding an open evening in the clubhouse from 8pm on Tuesday when the new kit will be unveiled.