Stimson told BBC London 94.9: "I didn't see it coming. I was only speaking to the chairman a week before about next season in League One.
"But we didn't perform on the last day, other teams did and I was given the news no manager wants to hear."
Stimson made a quick return to football when he was appointed manager of Barnet this week. He replaces Ian Hendon who has now moved to Dover to replace Andy Hessenthaler, Stimson's successor at Gillingham.
Source: BBC Sport
Source: BBC Sport