I'd request a public apology both printed and stated at the next several auctions. 

If that's not happening I'd get witness's lined up and contact a lawyer for defamation of character.  In the farming community your word is important.  If people think you're a crook chances are you will suffer financial loss.

A public declaration by the auctioneer that you are a crook and not answered will hurt you forever.  I suspect that no matter what happens there will always be some that will say"well, you never know, he might have done it." 

I don't think you can ignore this or let it go, it's not a matter of punishment it's a matter of your future and how people will treat and react to you.