No threads have been deleted. Threads have been moved to the correct forums, and in cases where the users cannot get a clue about what forum to post in, the redirection is left off. We only do that as a courtesy when people err on occasion, but there are those who deliberately do it and we are less than sympathetic in those cases.
If we did not care what forum people were posting in, then we would have only one forum for everything. Think about how ugly that would be.