How to Find Something You Lost in an Airport

What to do, in order

Work out where it was lost, precisely, At security, it is the security operator. On the plane, it is the airline. Anywhere else in the terminal, it is the terminal operator.
Security trays first, if it was in one, Items left in trays are extremely common and are usually held at the security point itself for a period before moving on.
If you are still airside, go back, Physically returning is worth more than any form you can fill in.
File before you leave the building, Reports filed on site are handled differently from ones filed later online.

A security tray: The single most common airport loss for laptops, phones and belts.
The gate seating: Left when boarding was called.
A charging point: Plugged in and abandoned when the flight was called.

If you carry a tag in your bag, scan at reclaim before you queue, a strong reading means the bag is in the hall and the wait is normal.
Airports are large and full of metal. Do not expect a scan to work across a terminal; use it at close range to confirm rather than to search.

The first hour looks different depending on where it happened.

At security, it is the security operator. On the plane, it is the airline. Anywhere else in the terminal, it is the terminal operator.

A security tray is the most common. The single most common airport loss for laptops, phones and belts.

In the app: A pin recorded at the moment you were last there is what separates these cases. Read about Last-Seen Map.