If your device has been out of your site, under the control of a well-funded government agency, and you believe that agency to be hostile then the device is compromised and the only thin you can do with it is sell it on to someone else or destroy it.

For Sale: Acme XYZ123 laptop with <specs>. Confiscated and returned by Israeli airport security. Great buy for counterintelligence agents or someone looking for a target for hardware compromise detection practice.*

* The security of the laptop, electronic devices in its vicinity, or the purchaser is not guaranteed.

I wonder if selling it on eBay with that description would increase or decrease its value.

Never got my laptop back.

That wouldn't necessarily remove everything evil that could potentially be done with it though.

I don't think he has received his laptop yet

Still no laptop, and no updates from Turkish Air nor the airport.