Benjamin Franklin once said two aspects of life were inescapable: death and taxes. But according to a recent study by Lookout, a mobile security firm, he left one inevitability off the list: losing your cellphone.

The research, based on 2011 data compiled from the company’s more than 15 million lost-phone location app customers, projects American consumers will lose approximately $30 billion worth of phones in 2012.

During 2011, the company located 9 million smartphones, an estimated rate of one disappearing phone every 3.5 seconds. The study shows the average American loses their device 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,” said Lookout co-founder and chief technology officer Kevin Mahaffey in a company press release.

According to the study, one’s chances of phone-loss are directly related to location and time. The number one and number two spots where people most frequently lose their devices are coffee shops and bars, respectively, usually between 9 p.m. and 2 a.m.

On average, Philadelphia residents have the hardest time keeping up with their phones, while Nashville, at No. 30, boasts the lowest rank specified on the company’s list.

Not coincidentally, significant overlap exists between the top-ranking cities in Lookout’s analysis and the front-running municipalities in the FBI’s 2011 crime statistics. Oakland, Newark, Detroit and Cleveland were all in the top 10 for both lists.

“Crime is definitely a significant part of that dynamic,” said Verizon representative Cheryl Sallaway. “Most of the time, when someone is a victim of a stolen phone, it’s a product of how they carry themselves. I always tell people to manage your phone just like you manage a wallet or a purse.”

Sallaway said for phone owners looking to keep up with their devices, “most of it is just common sense.” She advised conscientious communicators to keep phones out of small side pockets, from which they may easily be stolen or dropped, and on one’s person, especially in crowded social situations.

“There’s going to be concern about how to get a new one, replacing old contacts and keeping others from getting information,” she said. “For many owners, losing a phone is a tense situation, but if you take measures to prevent it from happening and take the proper steps when it does, it’s not hopeless.”

Just for the record, I lose my cell phone at least 3 times a day! What about you?