The 46-year-old was not present at the Tony Macaroni Arena as he recovers from illness, with the West Lothian club reluctant to publicly expand on the nature of the ailment.
However, the Livi boss is expected to take training on Monday morning – and his players will still be on a high following another hard-fought triumph.
A Kyle Magennis wonder-strike ensured a nervous finale but Livi held firm to remain in third spot and extend their unbeaten run in all competitions to nine games.
Livingston claimed a deserved lead midway through the first period. Aymen Souda's corner found Lithgow completely unmarked in the box, allowing the skipper to head home his second goal of the season.
Prior to their visit to West Lothian, St Mirren's previous six games failed to bring more than one goal – so it already looked an uphill struggle for the Buddies.
The excellent Souda was inches away from doubling the hosts' advantage on the cusp of half-time when he showed super footwork to find space on the edge of the box before rippling the side-netting with a powerful drive.
St Mirren showed more industry after the break, with Jon Obika forcing Lithgow to block a goal-bound drive within minutes of the restart. The English attacker also nodded over the bar following some excellent work by Kyle McAllister.
That proved to be a false dawn as Livingston swiftly struck again. Chris Erskine surged to the byline and produced a pin-point cut-back for Dykes, and the former Queen of the South winger made no mistake from point-blank range.
St Mirren refused to roll over and pulled one back with 25 minutes left when Magennis curled a sensational left-footed drive beyond Ross Stewart from the edge of the box, affording hope to the boisterous band of Buddies who travelled from Paisley.
However, Livi held firm in the face of late pressure and even struck the cross-bar in the dying embers through Jack Stobbs.