Yes, good point. And if the disks are encrypted, you will definitely know about it, because they won't be getting any data without you. (Unless the email police broke AES or the key-strengthening algorithm and haven't told anyone yet. This is unlikely, however.)
On the other hand, Google has a lot of resources and lawyers to fight off the government if they come knocking, and they've been known to fight to the max in the past.
You? Not so much. If the FBI shows up at your door, you're toast.
Like this guy? http://w2.eff.org/legal/cases/SJG/
(Hint: the opposite. The government had to pay him damages for seizing his computers.)
Note: IANAL