Pulis' side fell victim to three first-half goals as Eduardo Vargas, Charlie Austin and Bobby Zamora put relegation-threatened QPR in command, with Joey Barton netting a fourth late on after Victor Anichebe had pulled one back for the hosts.
Barton had earlier been caught in the face by the arm of Youssouf Mulumbu in the 84th minute, with the West Brom midfielder sent off on a disappointing day for a side now eight points clear of the relegation zone.
Pulis told BBC Sport: "It just wasn't our day. First half we were awful and some of the goals we conceded were very, very poor.
"We just looked flat. The problem today is players listen to social media and media and they might think this is job done.
"But it isn't, we need points to stay in the league. It's a relentless league and, as I said to them afterwards, until you get over the line, you just can't take anything for granted."
Although Pulis accepted West Brom deserved nothing from the game, he took exception Mulumbu's dismissal and QPR's fourth goal.
"He's led with his hand but he's not pulled his elbow back and tried to smack him. It looks a lot worse than what it is," Pulis added.
"Their fourth goal shouldn't be a goal. Austin's actually taken Gareth's [McAuley] legs from under him [in the build-up].
"We have to move on. That's hopefully a rude awakening for the dressing room and everybody round the place that there's still a lot of work to be done."
