A four-game Premier League winning run ended with a 0-0 draw against the bottom team, whose goalkeeper, Julio Cesar, repeatedly thwarted the champions in stormy conditions.
The Brazilian denied Gareth Barry and David Silva with fine saves as City failed to close the gap on Manchester United to two points. Instead City is four points behind the leaders, who host Southampton on Wednesday.
"We did everything to win this game but we didn't score," City manager Roberto Mancini said. "When you play like this away and you don't win, it's incredible."
The draw came hours after AC Milan said it had reached an agreement with City to buy Balotelli, leaving Mancini with little time to strengthen his strike force before the transfer window closes on Thursday.
"It was difficult because I lost one striker, one important striker ... it's difficult to find a solution for us now," Mancini said.
"We need a defender now because we have one or two injured, but it's difficult."
Letting Balotelli return to Italy was for his own good after 2 1/2 years at City overshadowed by disciplinary issues on and off the pitch.
"It will be a good chance for him to stay with his family, to play for Milan," Mancini said. "I think he can improve and I'm happy he will become one of the best players in the world ... you can be upset with him sometimes, but afterwards he's a lovely lad."
It was Balotelli's unpredictably on the pitch that might have conjured up the winning moment at Loftus Road where rain swept across the stadium in every direction.
"The pitch was wet, it was windy," Mancini said. "It was difficult."
Such conditions could have made life difficult for the goalkeepers.
It was a quiet night for City goalkeeper Joe Hart, whose decisive moment came late in the first half when Adel Taarabt went past Gael Clichy and blocked a close range shot.
Cesar, though, was called on to produce save after save to frustrate City.
An early effort was punched clear from Silva, but Joleon Lescott could only send the follow-up over.
While Cesar was beaten in the 20th minute, Pablo Zabeleta's diving header crashed against the crossbar and Sergio Aguero sent the rebound wide of the target.
Cesar's quality was underscored late in the first half when he tipped Barry's shot wide.
"Cesar saved everything and we made some mistakes — on another day maybe we could have scored four goals," said Mancini, who signed the goalkeeper from Flamengo in 2005 while Inter Milan manager.
"Julio is one of the top goalkeepers in the world and he saved his team."
Cesar was one of three goalkeepers were in the QPR squad, with manager Harry Redknapp also putting Rob Green and Brian Murphy on the bench.
Rather than including youngsters among the substitutes, Redknapp appeared to be highlighting the need for chairman Tony Fernandes to strengthen the squad before Thursday.
"We're desperately short, really ... the chairman's working on several options," Redknapp said. "I've given him a list of players and he's trying to get one or two for us."
On the target list are Stoke striker Peter Crouch and Anzhi Makhachkala defender Christopher Samba.
"The chairman asked me a week ago whether I'd be interested if he could get me Samba," Redknapp said. "I've left it wholly in his hands. On Crouchy, we'll have to wait and see."
Redknapp has already persuaded Loic Remy to join from Marseille. The France striker was prevented by scoring against City when Javi Garcia's heel blocked his shot, and he was denied a penalty in the second half after going down following Lescott's challenge.
QPR has now conceded just once in its last four league games and at the heart of the defensive solidity has been Ryan Nelsen.
But the west London club is losing the New Zealander now as he heads to Major League Soccer to become coach of Toronto FC.
"I wish Ryan Nelsen would (stay), but I think we're struggling ... he will be missed massively," Redknapp said.
For now, though, Redknapp is savoring the point gained in the bid to survive the drop.
"We defended well, hit them on the counterattack a few times, and defended fantastically all over the park," he said. "It was another solid performance, a big point for us."