Spalding missed out in the last play of Saturday’s game, having trailed from the sixth minute.
They went behind when Sleaford sliced open the home defence to score under the posts for a converted try.
However, victory should have been snatched out of defeat at the end.
Awarded a scrum on the five-metre line following a knock-on at a lineout, Spalding secured the ball at the put in.
The home team’s forwards had the upper hand in the scrum and they started to exert their superiority, edging forward.
With the ball under control at the back of the scrum, five metres were steadily eaten away until the try line was within reach.
Finally the ball was over the try line and all that was required was for a Spalding player to touch down to win the game.
Instead, Sleaford’s scrum-half picked the ball up and cleared for the referee to blow his whistle to end the game.
Sleaford’s opening try had knocked Spalding’s confidence and the visitors capitalised as they spread the ball out to their backs.
A quickly-taken tapped penalty saw Sleaford’s inside centre cut through some poor defence for a converted try and a 14-point lead within nine minutes.
Spalding responded using a combination of forward play then releasing the ball along their backs and as left-winger Ben Shields received the ball, it looked like the move had finished. But Willis Ingleby was looping around and a good offload saw him score in the corner.
Spalding’s suspect defence again allowed Sleaford to immediately respond with their centres creating a hole for their outside centre to gratefully run through unopposed for a further converted try.
Within minutes, Spalding were attacking deep into Sleaford’s 22 and from a ruck, Harry Sharman sold a dummy pass and was over a second try with Ingleby converting.
Back came Sleaford and their right-winger was round Spalding’s failing defence for their fourth converted try with only 24 minutes on the clock.
Trailing by 16 points, Spalding had to dig in and use their forwards to hit back.
Carries from the front row trio of Jacob Greaves, Sam Cooke and John Barrett took Spalding back down the pitch and with Sleaford defending their line, captain Richard Cooke dived over for another converted try just before half-time.
Liam Adams came on for Harry Cole at flanker and Spalding’s defence sorted itself out.
In contrast to the free-flowing opening first half, the second period became tight and intense.
Sleaford were kicking deep for territory but this played into full-back Adam McHugh’s hands with his forceful counter-attack runs setting up good rucks for Spalding’s next phase of play.
Sharman showed the way with a forceful drive for his second try and set up Spalding for the last 15 minutes of sustained pressure.
Penalty kicks to touch brought no reward until the final few minutes of the match when an unlikely victory should have been secured.
Spalding’s consolation was picking up two bonus points.