NEW YORK TIMESBy Christine NegroniOctober 28, 2009 United Airlines learned its lesson the hard way that David Carroll was not just another customer.After baggage handlers at United broke his guitar last summer and the airline refused to pay for the $1,200 repair, Mr. Carroll, a Canadian singer, created a music video titled “United Breaks Guitars” that has been viewed more than 5.8 million times. United executives met with him and promised to do better.So how was Mr. Carroll’s most recent flight on United?This Everyman symbol of the aggrieved traveler was treated, well, like just another customer. United lost his bag.In an interview, Mr. Carroll said that for more than an hour on Sunday, he was told he could not leave the international baggage claim area at Denver International Airport, where he had flown from Saskatchewan. He said he had been told to stay because his bag was delayed, not lost, and he had to be there to claim it when it came down the conveyor belt.“I’m the only person pacing around this room,” Mr. Carroll said, recalling how he was caught between an order from United staff members to stay and collect his bag, and a federal customs official telling him he had to leave the baggage claim area. The bag never showed.A United Airlines spokeswoman, Robin Urbanski, said, “We will fully investigate what regretfully happened.”Mr. Carroll’s life has taken more surprising routes than his luggage. He enjoyed modest popularity as a singer-songwriter in Canada until his video, which has made him a sought-after speaker on customer service.His father-in-law, Brent Sansom, has become his business adviser to help him sort requests.This latest episode provided him with fresh material for his most recent performance, which was why he was flying on United — to speak to a group of customer service executives on Tuesday (though without his best shoes and “United Breaks Guitars” CDs that were in his still missing suitcase).When Mr. Carroll asked members of the audience if they ever had a similar problem, he saw a sea of hands.“It crosses all income levels and languages and geographies,” he said. “We all don’t like feeling disrespected or insignificant.”Greg Gianforte, the founder and chief executive of RightNow, a customer service software company, and the person who organized the meeting, said he was sorry to hear what happened to Mr. Carroll, even if it made for a livelier meeting.“We were thrilled to have Dave come here,” Mr. Gianforte said. “But since United was the only carrier he could take from Canada to Colorado Springs, in a certain sense, we’re responsible.”Mr. Carroll was reunited with his bag on Wednesday morning.