The best possible case would be someone who had airtight proof of owning bitcoins, that were later stolen. The stolen bitcoins then ended up on silk road through no action or fault of the original owner and ended up in the bitcoins seized by the FBI.
It would be interesting because a judge ruling that bitcoins are property and not a bearer instrument, would likely rule that nemo dat quod non habet applies. That would force the US treasury to return the stolen property. Even if the DOJ (acting on behalf of the US Treasury) had already auctioned off the silkroad coins, the coins could be taken from the purchaser (and I am sure the US Treasury/DOJ will keep good records).
So you could actually see the US Treasury and DOJ filing briefs stating arguing that bitcoins are a bearer instrument and that nemo dat quod non habet does not apply.