Is something supposed to be bolted here?

Yes, there is a bracket there that connects to the front of the car. Not sure how vital it is, but my 2010 has it.

 

Here's a pic:

 

Has your car ever been to the body shop for front end repair? Looks like the ol, “It don’t need it” repair.

 

Asked and answered.

Either a sloppy mechanic didn't replace it following an inverterectomy, or the car got socked in the nose in a previous life, and was repaired by some third-rate 'Beat-n-Bang Body Shop'.

 

Pretty sure this is it, but they don't make it easy:


G921447060 - Toyota Drive Motor Inverter Bracket. Upper bracket | Toyota Parts Overstock


This Canadian site has a better diagram (same part # for Prius v):


https://www.toyotapartsdirect.ca/p/Toyota__/BRACKET--INVERTER--No1-BRACKET/47982909/G921447050.html

 

Another link, just searching for the above part number:

Upper Bracket - Toyota (G9214-47060) | Toyota Parts

 

I compared the bolt on the black plastic piece, with a bolt on the hold-down bracket:



They're both 10 mm socket size (6mm dia at the threads), and the same thread pitch. Both taper down for about 1/8" at the tip. The hold down bracket is longer, about 36 mm from underside of bolt head to tip, and has a captured flat washer.


(Hold-down bracket bolt on right)

Found this in Repair Manual:

 

Again, what is the history; was there a collision repair? Maybe some body shop couldn't get the bracket to fit due to misalignment, so just quietly ditched it?

 

Wherever you're getting your bolts, bring along that one from the plastic piece: while it's shorter, it's the same diameter and thread pitch, so if you can find a metric nut that fits it, then check the nut fit on the bolt you're going to purchase. A dealership parts department would be the place to get the kosher bolt, correct part number, dimensions, grade. It'll also be pricey, but the safest route.