For the record, every thread that is deleted brings up a text box for the moderator to explain why the thread is being deleted. The explanation is sent out by the site, in which format I don't know, as I've never received one. Whether it says it comes from me, from NOOL or what, I don't know. Spotnick would be able to advise, no doubt.
You would have received one of these messages when the thread was deleted, explaining that the thread was one of several duplicates on the same subject. I know, as I typed the message myself.
This obviously should come to you, again whether it is as an e-mail to the e-mail address with which you are registered on the site, or as a PM to your message inbox on the site, I don't know. You may wish to check your e-mail account and spam folder.
If you want to think that this is some kind of personal attack on you, that your thread has been deleted unfairly or without sticking to the protocols of the site, then so be it. It isn't, nothing untoward has taken place.