I did ask if we can sign a contract,

they didn't reply positively because they have someone else interest at that time(the house was still available), but they didn't tell me anything even when I asked.
if they signed a contract before I asked, I wouldn't say anything, but I clearly express the intention to sign a contract and they even didn't ask me before they sell it to others, do you think it is fair to me? They keep all the information from me because they still want me to be a backup.