If you try with Search:jsontools error and By user:engkin, the post will appear.
It did not bring the missing thread, but it did show this one.
If you enable Search in topic subjects only, the missing thread will appear.
Yes, finally!!
Is this the intended behavior?
Imho, like explained in previous post, It seems that search is exclusive, or in content of post (default) or in title of post.
But not in both.
I find it a little strange.
(But all is strange at the moment).