Why does it say I can't view my subscription?

This crops up once in a while, I get a notification that there is a post in one of my subscribed threads, but when I try and view it I get this message.

[ATTACH=JSON]{“data-align”:“none”,“data-size”:“medium”,“data-attachmentid”:9973694}[/ATTACH]

if if I search for the thread though, I can view it no problem.

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You see this message when the post on the thread that generated the notification has been deleted. Because the post is no longer there, you don’t have permission to view it.

That I would understand, but the threads and new posts are there when I search, and I can view the thread OK. The first time it happened I thought it was a deleted thread option, but when I mentioned to someone about the thread disappearing they said it was still live, and they were right.

Deleted POST on the thread. Not the whole thread going poof.