With a warrant, they try and try but they just can't find your stash.
With a suitable search warrant, the police can tear your house apart to find your stash. You cannot legally prohibit them from opening your house, and you cannot stop them from executing the search warrant to the full extent of its authorization.
Encryption is the same way. The encrypted container is the house;
And likewise, you cannot prohibit them from opening the encrypted volume.
Then it's a decision for a judge to make. The judge would be the one to decide if, by not providing a password, you are violating the court orders. You can provide evidence for your story, and the police can provide their own evidence. If you claim that somehow you had a 50-gig corrupt file, and the police show encryption software and logs of file access on volumes that don't exist, you're going to have a hard time convincing a judge of your story.
A better analogy would be evidence locked in a safe. The police can see the safe and can infer that it holds evidence, but you can claim to have forgotten the combination, or claim it's an antique to which you never knew the combination, or claim that it broke. If you can make a convincing case, you have a shot. If the police have evidence that you opened the safe a day earlier, you're pretty much screwed.