You didnt have it parked.
Those are the rules.
This has happened to me once before. Only it was a $70 (Sedo took $50) I got $20.
My mistake, I should have had it parked, which I didnt. Buyer got domain, I lost $43. Way it goes.
To Sedo's credit, I have parked a new domain and had it sell within 24 hours and only got charged the $6 (on a $60 transaction) It is all automated, which is good.