You can think of the following actions ;
1. Sacrifice your 'ego', seek an appointment with your boss and offer a valid reason for your leaving the Company without Notice.
If no valid reason exists, pl offer him an apology and coax him to issue a fresh Termination letter.
2. Seek help of HR Manager or a senior level person of your previous Employer to play a go-between your former boss and you so that a fresh Termination letter be issued.
If the job market demands a good reference from your previous Employer , then you better patch up as soon as possible. This action will eventually come to your good stead.