What if the signature on blank paper is forged into an iou? If you don't know them at all, how can you get evidence to prove your innocence?
Apply for identification. If there is a certain time difference between the time when you signed the loan and the time when you forged the loan, the appraisal should prove that you signed it first and the loan was written later, but I don't know how long it will take to identify it, just to provide an idea. Besides, what's written on the IOU? You can also find loopholes in the content.