United would have made it three wins on the bounce were it not for a fine display and a last-gasp stop from stand-in keeper Joe Anyon.
If the prospect of a visit from the league leaders on New Year's Day wasn't a daunting enough prospect, Martin Foyle was forced to pencil out a team sheet without six first-team regulars.
And the depleted hosts were on the back foot within the opening ten minutes when a mis-judgment from Richard Walker let in Billy Sharp.
And the League One hot-shot needed no encouragement to pull the trigger but uncharacteristically smashed a wild effort into the travelling contingent.
Vale are without super-stopper Mark Goodlad for the rest of the season after he picked up an Achilles injury in the weekend's action, but in Anyon, Foyle has found a worthy replacement.
The young keeper, making his home debut, pulled off a quick-fire double to keep out Neil MacKenzie and Sharp in succession.
While the inexperienced custodian was blooming under fire at one end, the Vale frontline were giving the visiting number one plenty to think about.
The hosts would have taken a lead into the interval were it not for Joe Murphy's reflexes frustrating Jeff Smith and Akpo Sodje with the half-time whistle looming.
The Irish keeper was then forced to his acrobatic best to repel Michael Husbands' effort - a save which prompted plaudits from both sides of the ground.
After finishing the first half in the ascendancy, the home side needed 23 minutes of the second period to take meaningful aim on the Iron goal.
Marauding full-back Jason Talbot appeared on the edge of the box to smash a Michael Walsh long throw inches wide of Murphy's left-hand post.
Nathan Lowndes should have punished Scunthorpe when he sprung the offside trap in 84th minute, but the scampering flankman wasted two opportunities to centre for the unmarked Sodje.
United should have taken the spoils at the death when Andy Keogh found the usually clinical Sharp unmarked at the back post but Anyon produced a superb low save.