First identify where you lost the item at Incheon Airport. For items left in public terminal or transportation-center areas, contact Incheon International Airport's Lost and Found Office. For property left onboard an aircraft or checked-baggage issues, contact the airline; for items on airport trains or buses, contact the transport operator.
According to the airport's current official lost-property page, Terminal 1's office is on basement level 1, west side, while Terminal 2's office is on basement level 1, east side. This corrects an earlier description that placed the T2 office in a second-floor government-service center. The official page lists operating hours of 07:00–21:30 daily for both terminals. Check whether an item has been registered before travelling: T1 +82-32-741-3110/3114; T2 +82-32-741-8988/8989.
Bring identification and details that establish the claim. Collecting through a representative or arranging delivery can require extra documents. Passports, phones and other special items may be handled differently. Reconfirm the exact location, rules and availability with the relevant office; no live lost-item inventory was verified.