Graduated High School Early, But . . . .

I would go back to an earlier save and try it again, since your Sim didn't get the things you expected from past experience. 

The diploma is being sent via mail and goes into the household inventory :) You have to move it into your teen's inventory from there. Alternatively, you can get it in build mode, though I think you have to pay for it.

Teens graduating early seems to be a feature of HSY. So far, every kid in my main household has been able to do that. The second one got the offer after only two days in High School. Yeah, no, not gonna happen. Get a proper education, kid.

The cheat never did work, so since it was really bugging me, and I always start each gaming session doing a Save As, I was able to go back in time and replay my story from there. This time, he ended up with the Trait. I will, however, take a look in the family Inventory for the missing diploma. Oddly enough, the last time I had kids in high school who graduated early, the diplomas did go straight into their personal inventory. So, once again EA broke something in their effort to add things. Knit one, pearl two, dropped a stitch right in my shoe . . . Thanks, I'll look for it the next time I power up my game.