A federal security director says they're relatively confident that it "got scraped into the trash, and it's gone."
The agency has spent several days trying to determine what information was on the drive and where it had gone.
The device, called a ThumbDrive, turned up missing Oct. 16 at the Transportation Security Administration's command center at Portland International Airport.
The agency has about 500 employees statewide who oversee airport security checkpoints.
When the device was last backed up a month ago, it contained the names, Social Security numbers, addresses and telephone numbers of the current workers and roughly 400 former ones in Oregon.