Air carrier Flight Attendant reported a passenger's cell phone was lost in the aircraft fuselage during boarding. After maintenance was unable to locate the missing phone the Captain elected to complete the flight.

Narrative

An ON phone inside the fuselage.FAs were asked to choose between working the flight feeling unsafe and at risk or getting off and getting a missed trip and 3 points. When close to the end of boarding; passenger informed an FA that his phone fell on the left side of his seat and went into the fuselage and was now out of sight. Captain was immediately informed. After a few minutes; a mechanic stated he did not find the phone and that most likely it fell into cargo. All the FAs expressed their concern for their safety and that of the passengers' stating the following valid reasons: 1) Customers are asked to take lithium batteries out of their checked bags SAFETY CONCERN: now there is a cell phone inside the fuselage. 2) Precautions are taken when lithium batteries will be in cargo SAFETY CONCERN: the cell phone in the fuselage exposed risk as it was ON 3) An FA shared she recently mailed through USPS a phone; the clerk reported to her that the shipping would not be done by air as it posed risk; and instead it would be by ground. SAFETY CONCERN: if the post office stated a cell phone would pose risk if shipped by air then the cell phone inside the fuselage posed risk to 374 souls onboard. 4) Another FA reported that on a previous flight; a cell phone went into the fuselage and all efforts were made to find it. All bags in cargo were taken out and the cell phone was found. SAFETY CONCERN: the search took a few minutes and it was decided for the flight to depart. Captain stated it's been decided for the plane to take off. 5) FAs were asked to choose between working the flight feeling unsafe and at risk or getting off and getting a missed trip and 3 points."