The problem is when they disappeared. For hundreds of years, the Ricardians falsely claimed that they didn't disappear until Henry VII became king. When Mancini's diary came to light in the late 1930's, the self-serving claims of Ricardians that the date of their disappearance was never firmly established during Richard's reign were demolished once and for all.
Contemporaneous accounts of their disappearance -- and much more importantly, the public knowledge of the fact of their disappearance -- lead to only one conclusion: they disappeared when Richard was King. The countryside was against Richard, and not just the Tudors, as Ricardians like to claim. The disappearance was one of Richard's problems among his countrymen. He could easily have made that problem go away... but only if his nephews were still alive.
I never thought they disappeared when Henry was King, since the wealth of evidence is for an earlier disappearance-and I haven’t read that book some people are referring to.
I don’t think if I had all of Richard’s problems-one of them was the disappearance of my brother’s two kids, and I had paid to have a friend somewhere on the continent abduct and keep them there and out of my way-obviously I’ve committed a crime. No way in hell would I produce the kids, or say oh well, I sent them to the French Pyrenees to be kept incognito by Comte de Whatever so they don’t get used to take me down, sorry about that. That would almost certainly have gotten him into his last battle a lot faster than it happened.