The argument is not that you shouldn't read the small print - the bank lawyers know what the small print means - the argument is that they can't look for tiny changes in known small print if they're reasonably expecting it to be identical to what they sent.

That's like I would initiate a contract with you and after we read it together and you agree it's what you want to sign I covertly slip a page into the pack that completely changes the terms and trick you into signing it without you actually knowing it's there. You can reasonably claim you intended to sign the original one, not the one I secretly modified - and I expect the court be more sympathetic to you than to my claims "you should have watched my hands all the time!" Of course, it'd require you proving that I did this, but if you can, your case sounds pretty strong to me.