Players are allowed a maximum of 14 clubs but Austin discovered he had 15 while playing the third hole and reported it to a rules official.
Rule 4-4 states: "The player must not start a stipulated round with more than 14 clubs." The penalty is two strokes for each hole at which any breach occurred, with a maximum penalty of four strokes.
Austin added two strokes to his score for the first and second holes, turning a par and a bogey into a double-bogey six and triple-bogey seven respectively.
The 49-year-old had started the day just four off the lead after an opening 69 and despite birdies at the fifth and sixth, was now in danger of missing the cut after further dropped shots on the ninth and 10th.
His blunder rekindled memories of Ian Woosnam at the 2001 Open, with the Welshman penalised two shots while challenging in the final round after discovering an extra driver in his bag on the second tee at Lytham.