Americans lost $30B of mobile phones in 2011

— -- Americans lost about $30 billion of mobile phones last year, says a report from mobile security firm Lookout Labs.

More phones were lost in Philadelphia than any other U.S. cities, says the report, based on data from 15 million users who downloaded Lookout's app that locates lost devices.

San Franciscans and New Yorkers lose their phones three times more than Chicagoans, it says. Top five cities in the U.S. for phone loss during 2011 are: Philadelphia; Seattle; Oakland; Long Beach, Calif.; and Newark.

The study points out that four of the ten cities with the highest rates of lost and stolen phones - Cleveland, Detroit, Oakland and Newark - also were among the ten cities with the highest crime rates.

Last year, Lookout's app located 9 million lost smartphones, or one phone every 3.5 seconds. Based on the sample data, Lookout concludes Americans lose their phone, on average, once a year.

"Each day, $7 million worth of phones are lost by Lookout users alone, and if unrecovered, it would take a significant toll not only on our wallets, but on our psyche too," says Kevin Mahaffey, co-founder of Lookout.

People are most likely to lose their phone at night. A large majority of lost phones - 67% - are located between 9 p.m. and 2 a.m. local time.

Phones were most often lost at coffee shops, bars, work places and restaurants. In New York City, fast food restaurants topped the list of places where phones are most likely to be lost. In San Francisco, coffee shops topped the list.