Lost watch and are new activities sync to my account?

7902505 said:

What would happen if they performed a factory reset on the device? If the watch is still linked to my Garmin account, would I continue to see any new activities recorded on it?

That would be extremely unlikely. For activities to appear in your Garmin account, the watch would need to sync either via Bluetooth, meaning it has to be within Bluetooth range of your phone (about 10 m / 30 ft), or via Wi‑Fi using a network already saved on the watch. Unless the watch comes near your phone or one of its saved Wi‑Fi networks, any activities recorded on it won't be uploaded to your Garmin account.

Your best option is to continue working with the airport's lost-and-found department and, if appropriate, local authorities.