It depends on how obvious it was that this was a disclosure form or not. If on the face of it, it was or should have been obvious, then you can be held to it--people are expected to read what they are going to sign before signing. If it was not obvious (e.g the disclosure terms in "small print," hidden, obscured, etc., however, it may be that  it is unenforceable...and if the form/sheet nowhere indicated that it was a disclosure form (i.e. it wasn't merely inobvious, but it simply was *not* a disclosure form), then you cannot be held to have agreed to the agency: a realtor cannot take a form signed for one reason apply to a wholly unconnected one.