Well, all things we don't see with with our own eyes leave us only with words from the others anyway. So it's up to each one to believe or not.
Personally, I watched the fight live and I was crazy about Vitor not using his hands and I posted about that in real time, if I remember well. I don't have a reason not to believe in his word for this particular issue.
Actually he broke his hand before the TUF finale against Wand (UFC 147)and apparently, the healing process was not good.
This is like the people that don't believe Silva was injured against Sonnen in their first fight. Lots of signs point to injury in both cases and yet people won't accept it because there wasn't a doctor stating it one way or another.
Jones is a great fighter but honestly I don't think he is as good as he is made up to be. Almost all his opponents are tailor made for his style(he is great against wrestlers) and the rest have been past their prime or lacking in some specific regard whereas Jones is pretty good all around.
This is one of the big reasons I want to see Jones fight Silva or at least Gustaffson instead of continuing to fight middle weights etc.
In Jones' defense he has pretty much wiped out the division(besides Gustaffson and perhaps Hendo), there just isn't that much other top talent at LHW right now. Time for some new blood to hopefully pop up or the division is going to get pretty boring.