Looks like the upper idler pulley is what came off. I see on the late model website they call out all 4.6 from 1996 to 2004 and is a motorcraft part.
I am sure the local auto zone or advance auto would have the same in a dayco or other brand replacement if in a jam.
https://lmr.com/item/LRS-8678C/96-04...MaApetEALw_wcB
I looked on advance's website and found a motorcraft unit and it shows the bolt (which I assume you lost also) coming with the pulley - maybe the route to go.
https://shop.advanceautoparts.com/p/...idler%20pulley
Hope this help!