Is there any such thing as a seller rejection letter?

[Laura Richards]

I have a strong suspicion that a sellers agent has lied about submitting my clients offer to her client due to the fact that my client was not represented by a agent and wouldn't agree to let this agent represent client on the buyers side too. Before I got involved, the sellers agent went so far as to tell my client that it is illegal to represent yourself in a real estate transaction. Due to that unethical behavior, animosity and tone of correspondence I read between the two (not by my client) I would like some way to confirm that the offer was actually submitted to seller.  

I could certainly create a document that I want the seller to sign evidencing the offer was actually submitted and rejected, but I am wondering if that is a normal course of action or is it something you just live with and move on? Is there a standard document or course of action agents use in this scenario - other than reporting her to licensing boards?