Suspicious, true. But in such case, you could be in trouble for refusing to provide the password to a suspected hidden drive which doesn't exist. How does that even make sense? (Rhetorical question)
From your point of view, it doesn't of course. You know that you don't have an encrypted partition.
But from the authorities' point of view, they will beat you until they're convinced you don't have anything of interest you can give up. That could last quite a while...
Which means that you can rot away for life, based on a LEO's hunch. And that's not The Sovereign People's Republic of Elbonia: that's Australia and the UK.
