welp...I got him!
I secured a rat trap to the board and the rat took the bait! If you look at the 1 o'clock position of the tub, you will see the rat as it fell off the board. Apparently, as he pushed on the lever and the trap sprung, he jumped backwards but was not quick enough. The trap bar slammed right across its face. I found the rat on the ground on the left side of the tub
the light kinda washes this pic out but you can see me holding the DEAD rat by the tail!