The handset was, however, found a couple of days later from a baggage handler working at the IGI, airport sources said.
Rahul noticed that his handset was missing from his bag after he returned home from the airport and informed the officials of the Special Protection Group, which guards him.
The SPG then contacted the CISF, which in turn started a quiet investigation and reviewed the close-circuit TV footage, the sources said.
The technical surveillance carried out by the CISF helped them detect the lost mobile phone.
The CISF personnel identified two baggage handlers as suspects and questioned them. One of them accepted that he had stolen the phone from the baggage and handed it over to the security personnel, the sources said.
No case was lodged in the incident as it would have brought the matter into limelight, they said, adding that the instrument contained personal and official numbers and other information related to Gandhi.
The sources, however, refused to give details about the flight Gandhi took or the date and time he arrived here from London citing security reasons.
They said such incidents were now occurring frequently at the IGI Airport and steps were being taken to contain them.
"We have taken the matter seriously. We have spoken to the airport authorities and the airlines regarding background checks before recruiting baggage handlers," the sources said.