My opinion for what it's worth... for $20 bucks I would just clean it up best you can. If it's still too icky toss it and find a consignment store to get a new one.
I would post a negative post about the condition of the item you received.
Personally I would never ever in my life have sent that or sold that to someone. I would have been mortified to send someone something so nasty. Can you imagine .....nevermind... So sorry, unfortunately it's the risk we all face when shopping online.
Sad that people do that.