I feel your pain.
Has anything happened in your relationship before this, that would lead him to have such trust issues?
I know lying is totally wrong and it should not have happened. But, you have been together for 15 years! He is ready to throw it all away over a stupid mistake? Is he perfect? Never made a mistake?
I just think there is more to this - because he is way overreacting.
I would not let him be. You need to show up and let him know that you are sorry for your mistake and you want to work this out. When he turns his phone back on - his voicemail should be full with calls from you. If he feels wronged by you - you have to show that you are sorry and will do what it takes to make this up to him.
Does he not have a job that he has to go to everyday? How can he just go out of town at the drop of a hat?
Good LUck