The reason that you've never seen Salvia flowers like that is because that is a Campanula, likely Campanula glomerata and not Salvia at all. So, you had good instincts thinking that it looked really different.
One thing to remember is that plants are classified by their flower structure so if the flowers don't look like Salvia flowers (or whatever particular genus you're trying to ID,) then it probably isn't one.
You still got a gorgeous flower, though!
I love the looks of them, but Campanulas generally don't like it here in the steamy south.