Pompey were unable to halt Lincoln’s unbeaten record on home soil – becoming the 12th side to take a League One point at Sincil Bank this season.
But John Mousinho was happy to see that his men were not content with a goalless draw following the final whistle.
The game exploded into life in the closing stages, with Colby Bishop and Ronan Curtis both going close to grabbing a winner.
Matt Macey also made a couple of saves at the other end, although Mousinho felt that victory was within Pompey’s grasp.
The Blues boss said: “It feels like two points that have slipped away and there’s a lot of disappointment in the dressing room.
“That’s natural when you finish the game like we did and we were on top in the second half, but couldn’t quite put those chances away.
“We had the opportunity to end Lincoln’s unbeaten home record and Colby knows he should be scoring – I don’t need to tell him that – while it was an excellent save to deny Ronan.
"It feels like two points that have slipped away and there’s a lot of disappointment in the dressing room."
“We weren’t organised enough at the start and Jack Diamond was causing some problems, but once we sorted that out, we were largely comfortable.
“The big positive is that we’re so disappointed not to win because so many teams will come here and be delighted with a 0-0, but we’re not.
“That shows the ambition of the players in our dressing room and where they want to go, while there were plenty of good performances to provide positives to take into next week.”
Experienced midfielder Marlon Pack has missed the past couple of games and is set for an extended spell on the sidelines.
Mousinho said: “Unfortunately, we’ve had a bit of bad news following a scan this week and it looks like it will be four-six weeks with his knee.
“We want to make sure we get the right so that we have him back on the pitch before the end of the season.
“It’s a big blow because he was our captain and had been playing really well – I know sides were looking at stopping us by stopping him.
“But we’ve got some very able players in the squad, as you saw with Joe Morrell dropping into the ‘six’ and producing an excellent performance against his former club.”