Lemon Symmphony is a form of African daisy, osteospermum, and I found it under "symphony plant" and not "bush."

The link I found is a writeup done by P. Allen Smith about this Proven Winner plant.

Since you did not describe what the plant you saw looked like, I'm wondering if this is in the right ballpark?
Maybe this can show us which symphony it is NOT anyway. :)

Here is a link that might be useful: Symphony plant

I just read a reply further down the board by Davey7 about a "moonflower bush"

Instead of linking, I'll jusut include it here for you. Since you think it might be a datura, this could be the thing you saw?

"IF YOUR MOONFLOWER BUSH HAS PRICKLEY SEED PODS AND THE FLOWERS POINT UP,IT IS PROBABLY DATURA INOXIA,WHICH WILL RETURN FROM THE ROOTS WITH MULCH EVERY YEAR. MINE COMES BACK BIGGER EVERY YEAR! HARDY TO ZONE 5, SO THE BOOKS SAY."
--Davey7