"Everyone was sobbing" after the show, says one of our "Idol" spies. We're told Pia was probably the most popular contestant among the contestants, and, "They were totally bummed out she was leaving."

The contestants -- sans Pia -- showed up for the "Kiss Off Dinner" at a restaurant in L.A. Pia made her entrance after everyone was seated ... followed by tears, more tears, and then one of the producers put it in perspective to make it all better, saying, "The point of 'Idol' is to launch careers. Pia, you're launched."

We're told Pia didn't check out of the "Idol" hotel last night, but she'll be out of there today.

UPDATE: Apparently, Pia ran out of tears, because earlier today she was seen out in L.A. with a big, fat smile on her face.