You shouldn't just roll over and let the mod get away with it.
Points of interest -
(a) deleting the first post deletes the thread - which is the problem. Not too concerned about posts past the first being deleted as only that post is deleted. If there are no posts other than the first post, and the thread subject is trivial or probably not of interest to others, usually I will let the deletion stand.
(b) I have no problem with thread deletions if there is a good reason - hence the suggestion to PM me with the details.
(c) if anyone has a problem with mod actions, simple redress is to complain up the chain with details. Airing angst in the thread is a waste of time.
Sorry if you feel put out ...