The shad are still in the river, just like the blues are still there... The flood water has moved their "comfort area". When you find the area that has what they need to survive, you'll find them.
I look in feeder creeks where the current is present, but not as swift as the main current. The shad will most likely be in the deeper channels during the day and up shallow in the lights at night.
When you find the shad, drop a baited hook to the bottom right there... you might just get a HUGE suprise!