1. The actions of the landowner is purely illegal as since the agreement was not completed and it was in the negotiation stage only he is bound to return the advance money paid to him.
2. So send him a a legal notice seeking refund of your money as under n circumstances once the agreement is not completed he can not withhold or forfeit the advance money.
3. If he does not return then file a case of cheating with the local Police as once FIR is registered you can expect your money soon.
4. There is remdey of civil suit also but the same is not cost effective.