I do see that tooth TJ. I also don't see anything that would prevent reverse. The transmission has been shifted once or twice no question about it! Lots of wear on the clutching teeth. If that is a piece missing from the input gear, something must have went through the teeth.

Scott, how do the teeth look? Does the input gear have broken teeth? Rotate the transmission gears and check all the teeth. The reverse idler needs a good look. Look at each tooth. If there are teeth missing on a gear that would be the issue. Does the cover shift properly on the bench?