Day 4 Edit
The SIM card of terrorist ringleader Habib Marwan was retrieved by Jack Bauer, Curtis Manning, and their field team when they captured Marwan. When Edgar Stiles analyzed it at CTU, he discovered a list of received calls, including the name of their next lead: Richard Heller.
Day 8 Edit
After Jim Ricker captured the Russian operative Pavel Tokarev, Jack Bauer interrogated Pavel for information about his superiors. Jack soon surmised that Pavel had swallowed his SIM card to protect his leaders. Partially because Jack was running out of time, and partially because Pavel had murdered Jack's lover Renee Walker, Jack disemboweled the man to retrieve it. The SIM card revealed to Jack that Pavel was in contact with Charles Logan, and soon led him to Mikhail Novakovich.