Jack Lester's first-half strike had given the Spireites an early lead but Wycombe goalkeeper Jamie Young was on-hand to save the striker's 47th-minute penalty.
And Chesterfield paid the price for that miss when Jon-Paul Pittman's injury-time equaliser salvaged a point for Wycombe.
Richardson said: "I thought we deserved the win, in the first half we controlled the game and with a little bit of luck we would have scored more than the one.
"The second-half penalty miss meant that we didn't have that cushion and when you are playing a team that has been up the top for most of the season they have that extra bit of belief that keeps them going.
"A bit of inexperience from some of the young lads has cost us and we got punished for giving away the free-kick at the end there but I can't fault the effort of the players."