Only one side had conceded more goals than Lincoln’s 10 in the opening four matches, so it wasn’t a shock to see yet another shipped inside eight minutes.
There was a touch of fortune to the opener, as a significant deflection helped Daniel Vasulin’s strike from just outside the box loop uncomfortably over Jaylan Hankins and into the net.
Sigma should have doubled their advantage straight after the restart, but Artur Dolznikov wasn’t able to adjust quickly enough to direct his follow-up into a gaping net after Hankins had parried into his path.
The hosts made the most of that reprieve, and they weren’t behind for long, netting a leveller in the 19th minute when a Nano long throw was met by Bernardo Lopes, who improvised to send a backwards header over a helpless Jan Koutny, who ultimately applied the final touch.
There was little goalmouth action for the remainder of the first half, but soon after the restart, Nano threatened the visitors' goal with a whipped free-kick effort that sailed just wide.
With the hour mark approaching, it looked for all the world that Sigma would retake their lead through Vasulin, but the winger could only prod Jachym Sip’s low ball off-target on the slide.
Incredibly, the Gibraltarian side turned the game on its head in the 73rd minute, capitalising on a loose ball in the box as Nicholas Pozo reacted first to put the unfancied side ahead.
Hankins kept the hosts ahead with a couple of important late stops, ultimately seeing David Campana’s side secure another impressive victory.
Three points for Lincoln sees them edge inside the top 24, having gone undefeated in their three home encounters (W2, D1) ahead of a potentially historical final league phase game.
Meanwhile, the result ends Sigma’s three-game unbeaten streak (W2, D1), but keeps them just inside the play-off spots.
Flashscore Man of the Match: Nano (Lincoln Red Imps)