Went out and looked at the front brake on my C5. Yes, you appear to be missing a part. There should be a guide pin on the end of the bolt visible in your pictures - it extends into that notched 'ear' on the opposite pad.
Neither of my paper catalogs show the part.
The pdf "Parts list" I have does not list it as an individual item, but part of the "Mounting Bracket Assembly" (p/n: 560583).