Brian Horton came back to haunt former club Brighton with an inspired substitution.
Adrian Littlejohn was among three players axed by the Vale manager after an embarrassing FA Cup exit at home to Scarborough.
The former Sheffield United forward was introduced for the second half in place of Austrian midfielder Andreas Lipa and he equalised within five minutes of coming on.
Littlejohn ended a jinking run with a 25-yard shot which sped past Ben Roberts off the greasy surface.
It denied third-placed Brighton a hat-trick of league wins after Leon Knight had given them the lead with a 16th minute penalty.
Premiership referee Rob Styles had no hesitation in pointing to the spot when Lipa brought down Chris McPhee and Knight calmly slotted home his 17th goal of the season.
Brighton deserved to be in front at the break, but the introduction of Littlejohn changed the game.
Vale almost snatched victory in the last minute when Littlejohn's fierce drive was parried into the air by Roberts and Stephen McPhee, following up, headed against the underside of the crossbar.
Brighton were also foiled by the woodwork in a tense finish. Zesh Rehman, on loan from Fulham, headed a cross from substitute John Piercy against the upright.
Horton said: "I am happy with a point and we could have nicked it at the end. I know Adrian can produce like that if he is on his game." Horton was unhappy with the penalty award by Styles saying: "All my lads are adamant it was not a penalty. It will be interesting to see the video.
"I had a side bet with Rob about it for charity as we walked off." Brighton manager Mark McGhee was not too disappointed by his team's failure to close the gap on Plymouth and leaders Queens Park Rangers.
"Every point at the moment is a point gained," the Albion boss said.