Paixao saw a wondrous 35-yard volley crash against the underside of the crossbar and - according to television replays - over the line less than three minutes after kick-off.
Team-mate Dougie Imrie had a penalty appeal turned down as Accies had the better of the first half, but the tide turned after the break and Higdon failed to net on four separate occasions.
The result denied Hamilton a fifth straight win, as well as mathematically ensuring Saints' survival.
Goalkeeper Mark Howard made his first appearance for a year as the visitors made four changes.
With his side having all but secured their SPL status on Saturday, Saints boss Gus MacPherson also recalled Lee Mair, Garry Brady and Higdon and named only five substitutes.
In-form Hamilton selected an unchanged side for their last home game of the campaign.
Tonight's game was James McArthur's chance to bid farewell to the New Douglas Park fans, with manager Billy Reid confirming this week the midfielder would almost certainly move to England this summer.
He almost enjoyed the ideal start, with Hamilton twice going close in the opening three minutes.
Simon Mensing's finish was straight at Howard inside 30 seconds after the keeper had palmed out Flavio Paixao's cross.
Paixao's twin brother Marco then unleashed a vicious, dipping 35-yard volley that crashed against the underside of the crossbar and over the line, though it was not given.
A beaten Howard hurt himself colliding with the post but was fine to continue after treatment.
The visitors went close themselves in the 15th minute when Billy Mehmet's flick-on was volleyed just wide from an unfavourable angle by Stephen O'Donnell.
Alex Neil and Higdon were both booked five minutes later for squaring up after the latter cynically chopped down the Accies captain.
Indeed, for a game with so little riding on it, there was no quarter given from either side.
Imrie twice screamed in vain for penalties in a seven-minute period just past the half-hour mark, the second appeal following what appeared a clumsy tackle from Buddies captain John Potter.
Both were waved away by referee Iain Brines, but the official soon awarded Hamilton a free-kick on the edge of the box, which Martin Canning headed wide from Marco Paixao's dangerous delivery.
Imrie exhausted Brines' patience moments before the break when he was cautioned for a foul on Hugh Murray.
Howard got away with seeing his clearance charged down by Imrie two minutes after the restart before Robb became the fourth player booked following a late tackle on Flavio Paixao.
Higdon then missed three great chances to give St Mirren the lead in a four-minute spell, starting in the 50th.
First, he nodded Graham Carey's corner against the post.
Then, after outmuscling two defenders, he saw Sean Murdoch fail to keep out his low finish before being rescued by Mark McLauglin's goalline clearance.
Finally, he bulleted a header too close to the keeper from Carey's excellent cross.
Hamilton produced the best move of the match just past the hour mark, slickly releasing James Wesolowski down the left.
The Australian's cutback was perfect for Mensing, whose low finish was blocked.
Great technique from McArthur saw the midfielder send a 20-yard half-volley just over the bar midway through the half, before the visitors introduced Rory Loy for Brady 20 minutes from time.
With less than 15 minutes remaining, Higdon failed to capitalise on another great chance, with Carey again the provider.
The full-back's first-time volleyed cross dipped perfectly for the striker six yards out but the former Falkirk man was unable to control it.
With just over eight minutes remaining, O'Donnell sent a looping header just too close to Murdoch from Robb's cross, two minutes before visiting boss MacPherson threw on Craig Dargo for Murray.
But it was Hamilton who went closest to a late winner when Trent McClenahan's 20-yard curler was beaten away by Howard two minutes from time.