I'm using the app on iPhone and we used to get a message with a reason why a thread has been deleted, but now it's gone back to the way it used to be where the thread just disappears without explanation. It's no longer in watching/I'm on. It's really annoying!
I've had a look around, and I can't find a deleted thread along those lines (we get a lot). However I've double checked some more recent deleted threads like this one or this one, and they both show the deleted thread response on the app.
If you do find any deleted threads without a message and have either the exact name or, even better, the URL for it - I can get to the bottom of it!