Buckner was awarded a penalty stroke on 22 minutes after a defender stopped his searing goal-bound shot with his knee.
But after spotting there was no marked penalty spot, Buckner raised concerns with an umpire.
After disagreeing with the umpire's suggested distance from goal, Buckner was yellow carded.
It was a disappointing end to a solid first half from Saxons who paid the price for failing to convert several chances.
In the second half the hosts were gifted the lead when debutant Joe Lovell tapped the ball into his own net.
Crowborough grabbed two goals on the break to put the game beyond Saxons as they began to tire.
Buckner said: "We bossed the first half but ran out of steam in the second. My sending off made no difference but I will never forget my discussion with the umpire."
Harry Dyas was man of the match