Hit a stump, bolt fell out, now blade/pulley area rattles loudly

I was mowing at 2.5" and nailed a hidden stump, hard enough to almost knock me off. Backed up and found the bolt in the picture in the grass. Grabbed it and when I resumed mowing there's a loud rattling below me and to my right around where the pulleys are. I jacked it up and blew off all grass/debris that's obscuring bolt locations and can NOT for the life of me find where this thing goes. Any ideas?

Thanks!

Brian

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