Unless you're a religious fundamentalist that is.
If you are, you'd immediately recognise this argument as identical to the one you very probably use when confronted by Atheists. Almost invariably, you'll insist your god exists and challenge them to prove it doesn't, then claim it must exist if it can't be disproved.
If you're an honest religious fundamentalist, that is.
If you're a dishonest one you'll deny your argument is identical in logic to my silly hippo-in-my-loft argument and then try to bring in other arguments, change the subject and avoid dealing with the logical fallacy you've been caught trying to get away with.
Actually, it's not so much a logical fallacy as a dishonest tactic designed to overcome the fact that the perpetrator believe in something for which they have no supporting evidence. It betrays the fact that they know they have as much evidence for their god as they have for fairies, or I for my undetectable loft-hippo.
It's called shifting the burden. It's the tactic of making a claim you know you can't substantiate and then trying to divest yourself of the moral obligation to substantiate it. It's no different morally to going into court and claiming the accused is guilty, then challenging them to prove their innocence because you know you have no evidence. Another name for this tactic is 'bearing false witness'. It's implicitly claiming you have evidence for something for which you know you have no evidence.
Some examples of fundamentalists bearing false witness can be seen here:
For example, 18.How do we know the supernatural does not exist? The answer of course is that we don't. Dr Saunders is implicitly claiming it does and divesting himself of the responsibility of substantiating his claim, almost certainly because he knows he can't.
Dr Peter Saunders. Twenty questions Atheists struggle to answer
Here's the great Mat Dillahunty dealing with someone who's trying it on him:
To be fair to many fundamentalists, they probably don't realise they're being intellectually dishonest. They're probably just aping the tactics of the charlatan who fooled them with it in the first place and lack the intellectual integrity or ability to analyse the tactic and see it for the trick it really is.
You can see these unfortunate people almost daily rushing onto Twitter, Facebook, or other social media eager to try out their new killer argument having seen one of their heroes use it.
Hopefully, this article will help them see where they've been fooled and maybe come to terms with the fact that this is probably their best 'argument' for their god's existence and it simply serves to highlight the fact that they don't have one.
So, here's my top tip for fundamentalists who may be tempted to try this shifting the burden trick. If you can think of a logical reason why my claim to have an undetectable hippo in my loft isn't proven just because you can't disprove it, neither is your claim proven by me failing to disprove it. Your claim to have a god is only proven by you producing definitive, authenticated and indisputable evidence for it. Just because that is impossible for you does not excuse trying to fool people with a dishonest tactic and false witnessing.
If you ever feel tempted to try the shifting burden trick because you've been caught making a claim you can't justify, try changing the word 'god' or 'life after death' or 'sin' or 'soul' or whatever daft idea you're trying to get away with, for 'undetectable hippo in Rosa's loft' and see if it convinces you. If it doesn't, your trick won't fool normal people. It might fool another fundamentalist but that's kinda cheating. The tactic will simply betray your moral bankruptcy and the fact that you know you are making a false claim. The only way to escape that charge is to believe in my undetectable hippo, fairies, all the gods other people do or have believed in, pink unicorns and any daft notion you or anyone else can dream up because no one can prove a negative, which is why the trick is so beloved of religious apologists who need to earn a living somehow.
Of course, this will render you incapable of living a normal existence without close adult supervision but that's the price you may have to accept to avoid the charge that you tried a deception and failed to get away with it.