Yeah, Tenki's probably right... I'm going to try this out a little bit more to see if I can do it again, but if not, I probably just started seeing things. It happens sometimes, when you play brawl at 11 30 but its 6 30where you were yesterday >.>
Well, yeah, I just tried it for a while and I sent DDD at a slightly downwards angle twice, but I don't think I hit with the full brunt of the attack cause it was weaker than it should've been, even though I hit with the initial hitbox. Even if its not DI, it most likely won't be useful at all, and I haven't gotten an actual spike yet. Sorry for posting before testing it fully, but I guess this thread will be up in case a fluke like this happens to someone and they can record it. And if you still want to test it, post your findings here, even though its most likely not worth your time to test it.
EDIT: I tested it this time on jump, so I doubt there would be downwards DI, but who knows. I don't remember what I tested it on before.