Flare Blitz is actually a multi hit move - there's a weak hit first and then a more powerful explosion it links into upon contact.
....However I don't believe either hit is supposed to be a projectile, so that is very strange. You sure he didn't just bumb into an item or something?
It all happened so fast, so maybe I did miss something; didnt seem like anything was hit though.
I've played through classic a few times with Hero (mostly using it as a way to get better with him since it scales in difficulty with each match) and there's been no time where any items spawned on that final battle.
It was just me and the Giant Charzizard, I used the command special, got Bounce off right before he used Flare Blitz. I heard the 'tink' sound of something being reflected off Bounce and Charizard fell over. It's not like we were off stage or anything; nor is there any other hazards for him to hit.
Maybe somebody can test this?
EDIT: Ok, I didnt realize I could control another player in Training.
A part of Flareblitz
is reflected, but not all of it.
After testing it in Training Mode, it looks like after Reflection, Hero takes 7.2% (instead of a normal 28.8% if hit) and Charizard takes 39.6% (instead of the typical 6% of self-inflicted damage)