Threads that are found to essentially be spam are often summarily deleted right away. I agree that it would be polite of us to PM the author after deletion and will ask the other mods to do so.
But sadly, which threads are spam and which are not, is a question that its entirely up to us mods to decide. Its not very democratic, but its the way it is. But if you disagree and present a good argument why, then perhaps your thread might get restored