Buttner says he was shocked by Ferguson's retirement last month.
"Everyone was taken aback by his decision. The trainer spoke to us all at the end of the season," Buttner told Voetbal International. "The words of Ferguson I will not soon forget. He called my development fabulous. That gave me such a kick."
On his Oranje snub, Buttner added: "It was a big disappointment. I'm very honest. After last season I received a nice reward. Unfortunately, it is not too late. I will not give up and will show that I deserve a chance in the Oranje."