Sorry if this is stating the obvious it just hasn't been said, could it be a communication between someone and the person who claims to hold the tax return i.e:

Person who claims to hold the tax return via letter to media: blah blah we've got Romnys tax return blah blah
someone: prove it
Person who claims to hold the tax return: www.imager/i....

......either making it look like they tried, ran out of bitcoins, or got bored halfway through posting link.