The Potters conceded two goals in the final 20 minutes to surrender a lead at the Vitality Stadium as Lambert lost for the first time since taking over following the sacking of Mark Hughes.
Goals from Cherries substitutes Josh King and Lys Mousset sent City back into the Premier League relegation zone after Xherdan Shaqiri had headed them ahead early on.
Asked if Stoke should have taken something from the game, Lambert, who was particularly frustrated that Mousset was left unmarked to head the winner from a free-kick, replied: “100 per cent.
“Listen I would have been absolutely disappointed leaving with a draw so I am absolutely gutted that we’re going away with nothing because we never deserved that.
“I thought we looked great for about 70 minutes, the equaliser I can understand because it takes a ricochet off Joe Allen that falls into the lad’s path, which can happen, but the second goal is unacceptable.
“Everything was great, we looked really good, the way we played, the style we played, the hunger, everything I asked of them.
“The second goal’s the one that’s really hurt us.”
Southampton’s win at West Brom and a draw for Swansea at Leicester meant the Potters returned to the bottom three on goal difference.
Asked how the mood was in the dressing room following the damaging defeat, Lambert added: “Pretty quiet, the way it should be. It’s normal I think when you lose.
“The lads know they played well and that’s the positive to take out, they came here and we played every so well. It’s the second goal that’s annoyed me the most.”
Uwe Rosler was sacked by Fleetwood following a 3-0 reverse at Doncaster which condemned Town to a seventh straight defeat in all competitions.
Cambridge interim head coach Joe Dunne was pleased with how his side adapted to beat Grimsby 3-1.
Southend manager Chris Powell led the applause for Jason Demetriou after the right-back scored twice in the 3-1 win against Portsmouth at Roots Hall.
Morecambe boss Jim Bentley was the happier manager after Gregg Wylde's 90th-minute strike earned his side a point in their 1-1 draw with Forest Green.
Manager Gareth Ainsworth described Wycombe's 2-0 win at Cheltenham as a thoroughly professional performance.
Skipper Richard Wood scored the winner just before half time as in-form Rotherham pulled off a 1-0 victory at League One leaders Shrewsbury.