MELBOURNE (Reuters Life!) - An Australian restaurateur left holding a hefty unpaid bill when five young diners bolted used the popular social network website Facebook to track them down -- and they got their just deserts.

Peter Leary from seafood restaurant Seagrass on Melbourne's Southbank was fuming when the diners ate their way through the menu, pairing oysters, trout and red emperor with some expensive wines, slipped out for a cigarette -- and never returned.

But Leary, left with an unpaid bill of A$520 ($340), remembered one of the diners asking about a former waitress, whom he then contacted and she suggested they check through some contacts on Facebook.

"We searched a few names and there in front of us his face came up," Leary told Reuters, referring to one of the diners.

"He was pictured with his girlfriend who was the only girl in the group. We also knew where he worked, at a nearby restaurant, which was handy. It'd been clear they were in the trade."

Leary contacted the manager of the other restaurant, where both the man and his girlfriend worked, and explained the situation.

Within hours the diner returned to apologize and paid the bill -- and left a generous tip for the staff.

Leary said the fellow restaurateur called him later to inform him that both the man and his girlfriend had been sacked.

"On this occasion I guess you could say that being on Facebook backfired for them," said Leary, who has no intention of taking the matter any further or contacting the police.

Facebook, which began in 2004 as a socializing site for students at Harvard University, has seen its growth zoom to 90 million members from 24 million a little over a year ago, overtaking rival MySpace to become the world's largest online social network.

($1=A$1.53)

(Writing by Belinda Goldsmith, Editing by Miral Fahmy)