My in-laws say that I divorced my wife through voice message while I was in a drunken state and I did not remember doing that the next day. Is the divorce considered valid?
Bismihi ta'ala
If that really was the case, and you are a Shi'i Muslim, then the divorce is invalid and has no effect.
There are numerous conditions for an Islamic divorce to occur, and from what you have said, none of them have been met. Therefore, she is still your wife.
You do need to deal with your alcoholism. As a Muslim, you know of its severity and how spiritually, morally and socially damaging drinking is.
With prayers for your success.