If I were him, I'd be tempted to make an image of his drive, and compare that to an image made after the agents tampered with it, to see what changes occurred in the process.
But like he said, he couldn't even trust them physically. I'd be tempted to just toss them in the trash, if I could afford to easily replace them.
Yes, you heard correctly. I remember a talk at a past LegalTech conference where the panelists urged anyone doing a lot of traveling (especially to 'sensitive' parts of the world) to simply travel with a 'spare' laptop, and keep everything important on encrypted USB drives, which can be sent through the mail in tamper-resistant packaging. It solves several problems:
1. Confidential data won't be compromised during a border search, theft, accident, etc..
2. You avoid the issue of being forced to give up your passwords to law enforcement.
3. If the laptop is confiscated, it can take months to get it back, so you wouldn't want that to happen to your main work machine.
Yes, some code has to be unencrypted to use the passphrase to decrypt the rest of the disk. People who are serious about security will boot off a known-good USB drive or CD.
Or just sell them, make back some of his investment, and have the people on the other end wonder why he's trading recipes or saying "OMG did you see that dress Kaitlin was wearing???".
But like he said, he couldn't even trust them physically. I'd be tempted to just toss them in the trash, if I could afford to easily replace them.