I enjoy your snarkiness daniel, but I think it's a bit more complex than "I'm so clever", FDE is a feature of MacOSX, Ubuntu, and .. I dunno.. probably Windows by now? Who cares.
They can essentially use all the tactics they would get you to use to reveal any other information, and if they have probable cause for that drive, the encryption keys are what they'll ask for.
Destroying them could put you in a tough situation, because they might not believe you destroyed them. Proving that nowhere in the world do you have access to a few kilobyte is pretty hard, and although the burden of proof is generally on the prosecution, it's up to them and law enforcement to interpret that outside of court. Because federal judges are protected by Federal Marshals - DOJ employees - they also have an IMO unhealthy relationship with the DOJ.
Full disk encryption isn't an "I'm so clever" excuse - take Ulbricht for instance even if he had shut down his computer before being arrested FDE wouldn't be help from someone asking his password. If you've been seen using the computer recently it's going to pretty hard to convince the courts that you don't know the FDE encryption password.
"I'm so clever" is running something that destroys all the data on your laptop and then claiming that you didn't do that in response to an investigation (and therefore obstructed justice).
Even with Truecrypt installed there's still plenty of ways evidence can be collected that can be used to demonstrate that you realistically have access to encrypted and hidden data. It isn't as simple as installing Truecrypt and thinking you're safe. Be it recently accessed documents lists for folders that don't exist, Truecrypt being installed, having software installed (and with recent execution dates) that don't have any corresponding data files anywhere on the system etc etc.
Think of it like Cold War espionage - you could live your life by "Moscow Rules" where you do everything possible to be able to claim, convincingly, that you're not being so clever. However even very talented agents and intelligence assets failed to not slip up on many occasions, and it involved huge amounts of time, effort and money on their parts.
They can essentially use all the tactics they would get you to use to reveal any other information, and if they have probable cause for that drive, the encryption keys are what they'll ask for.
Destroying them could put you in a tough situation, because they might not believe you destroyed them. Proving that nowhere in the world do you have access to a few kilobyte is pretty hard, and although the burden of proof is generally on the prosecution, it's up to them and law enforcement to interpret that outside of court. Because federal judges are protected by Federal Marshals - DOJ employees - they also have an IMO unhealthy relationship with the DOJ.