This sounds fishy to me.
No offense, but you must have done something seriously wrong to have been fired over a workplace policy. Privacy would suggest that your boss didn't tell anyone the reasons for you being fired, so is it possible people just surmised that you had been cheating with him?
Someone contacted your husband with specific information. Why would they do that, and pass on an unfounded rumour that would surely cause a huge rift in your marriage. And enough of a shock to your husband that he hasn't been home for four days.
It almost sounds like a confirmation to him that something was going on at work, and things weren't right. When you were finally fired, his worst fears were realized? Right or wrong, whatever he was told is somehow tied into you being fired.
Surely there must have been conversation between the two of you prior to all of this happening. Was he accusing you of having an affair? Were you both arguing about it? Is he an extremely jealous man? Was he looking for an excuse to leave because things weren't going well at home anyway, and this was a good reason?
Have either of you been unfaithful during the marriage?
More information would be helpful in figuring this out.