Sharpen, sharpen more and unsharp mask in PS actually only help to sharpen the blurriness. But once a photo is blurred, it is that.
In my thread on the Sunday Ballet Rehearsal, there are some "bloopers" of kids that I tried to save, all the same, for I had only got that one photo of the child or I much liked the child's expression in that specific photo and therefore did not want to trash that pic --- but the initial mistake (unwanted blur) will always be there, no matter how I tried.