The Kenwick Park GC member went into the fourth round of the leading amateur competition last Thursday lying seventh and in contention.
The trophy was formerly the South of England Amateur Championship, and boasts some illustrious winners, including US Masters champion Danny Willett who won it in 2007.
But an 11-over-par final round of 83 ended his hopes and dropped him to 27th in the 119-man field.
Seven strokes went on the front nine, and Done suffered a further bogey at 10, but an eagle at 14 followed three pars as he looked to salvage his round.
A bogey and birdie followed, but five strokes were dropped at the final two holes for an overall score of six-over.
The round was out of keeping with three consistently good rounds which had kept him firmly entrenched in the top 10.
Done, the defending Lincolnshire Open champion, followed up an opening level-par 72 with six birdies in a three-under par second round to lie eighth at the end of Wednesday’s play.
The good work continued the next morning as he recovered from dropping three strokes in the opening three holes to finish with three straight birdies in a two-under par third round, which also included an eagle and another birdie.