SPL Wrap: No winning start for new Inverness boss
Hughes was confirmed as Terry Butcher's successor on Thursday and he was unable to guide his new club to a fifth successive win against a St Mirren side who have now lost just one of their last nine games in all competitions.
St Mirren striker Steven Thompson struck the post in the first half, with second-placed Inverness also denied by the woodwork after the break to ensure Celtic's lead at the top of the table is now seven points.
In-form Dundee United secured a third consecutive Scottish Premiership win to move up to third in the table as bottom side Hearts were on the end of a 4-1 hammering at Tannadice.
Stuart Armstrong opened the scoring after 16 minutes, only for Jamie Hammill to equalise from the penalty spot five minutes later.
United were not to be denied and second-half strikes from Brian Graham, Gary Mackay-Steven and John Rankin sealed the points.
Kilmarnock secured their first away win of the season as Ross County were consigned to a 2-1 defeat.
Chris Johnston and Kris Boyd struck in the first half either side of a Stuart Kettlewell equaliser as Allan Johnston's side ended a run of four consecutive defeats to leapfrog their opponents, who are now second-bottom.
Aberdeen moved up to fourth place as goals from Peter Pawlett and Niall McGinn gave them a 2-0 win at St Johnstone.
A late goal from James Collins salvaged a 1-1 draw for Hibernian after Kris Doolan had put Partick Thistle in front at Easter Road in Butcher's first home game in charge of the Edinburgh club.