Striker Austin completed a ?1.2million move to Championship side Burnley on the eve of the game leaving manager Danny Wilson with Togolese Thomas Dossevi as his only recognised striker.
Swindon did not miss their 17-goal top scorer as they dominated the first half in which they could have scored on no fewer than four occasions.
Makeshift forward Matt Ritchie almost gave the home side the perfect start when he rattled Exeter's crossbar with a diving header after only nine minutes.
Grecians goalkeeper Ben Hamer then pulled off two superb saves in the space of a minute to deny first Jonathan Douglas and then the impressive Ritchie.
Midfielder Michael Timlin should have opened the scoring on 26 minutes when he was picked out by an Alan O'Brien cross only to blaze his shot wide. It took until the stroke of half-time for Exeter to seriously threaten Swindon's goal when Brian Harley smashed a 22-yard free-kick against the crossbar and the game ended goalless.