My husband got angry with me while I was at work, and when I checked my answering service, he left a message that I was divorced. Later that day he tried to catch me before I heard it but I already had. I told him that I would ignore it but I don't know if I can do that? Does this count as a divorce?

Praise be to Allah, the Lord of the World; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

If your husband has uttered the word "Divorce", as mentioned in question, then this is considered a divorce for one time. So, he can return you before completing 'Iddah if that is the first or second time. The 'Iddah means woman's waiting period after divorce or death of a husband. In other words, a pregnant woman's 'Iddah is to deliver; if not pregnant to wait for three periods of monthly menstruation; if one does not menstruate she has to wait for three months.
But, if such a woman completes her 'Iddah, then her husband can not return her except with a new contract of marriage.
If this divorce is the third one, then he can not remarry her unless she marries another person and has sex with him. Then if this latter one divorces her, it is permissible for the first husband to remarry her.
Allah knows best.