In a high-tempo encounter at Tynecastle on Saturday, United created the better chances against a fired-up Hearts side which failed to register a single shot on target.
Cadamarteri passed up a glorious chance from 12 yards when his weak effort was well saved by Marian Kello in the 61st minute.
Fourth-placed United are now four points adrift of Rangers in second and Levein insists losing further ground on the Ibrox outfit just before the two teams meet is a blow.
He said: "I think that's two points left behind rather than one picked up. I don't think we were great but Nicky Weaver did not have a save to make.
"I don't think that's ever happened with me taking teams here, we coped comfortably.
"Overall, I am a little bit disappointed we are going away with a point.
"Penalties can get missed, that's all part of the game. Danny scored his two previous penalties. I am disappointed but probably not as disappointed as Danny is.
"We were looking to get three points here and then we would have been on the coat-tails of Rangers if we had.
"I was hoping we could be in a position that we could get past Rangers with a win on Tuesday but that can't happen now."
Levein lavished praise on Andy Webster after the on-loan Rangers defender played his part in ensuring goalkeeper Weaver had a comfortable afternoon.
He added: "Andy gets better every week. I'm hoping about April time that we are talking about having had a fantastic season.
"Ranger's can't recall him, it's a season-long loan. That's what I talked about with Walter Smith at the start that Andy needs 40 games. He will go back a better player."
Meanwhile, Csaba Laszlo refused to condemn the fans that booed Laryea Kingston, whose commitment has been questioned by the Jambos boss, when the Ghanaian left the pitch five minutes from time due to injury.
Hearts had to finish the match with 10 men having used their full quota of substitutes.
Laszlo said: "I don't like to talk about this, I know which player I need.
"I like to protect my players. If someone is injured he can't continue, we didn't have the chance to bring on a new player, this was unlucky."
"I think we showed with 10 guys that we are a team.
"I don't like to comment, the fans would like to see for this club players that give everything and fight and have will."