do you find it reasonable that none of the flight recorders were found from the Tower collisions?
Here is the way I look at it:
1) The missing recorders are an oddity. Yes
2) The black boxes are generally pretty sturdy, so this adds to the obscurity
3) Now, I do study NTSB investigation a lot, out of personal interest and to learn from the mistakes of others, and I do know that the black boxes are not indestructable
4) There are many air accidents in which investigators cannot discern information from data recorders because the recorders have become too damaged
5) AA 11 and UA 175 with their data recorders hit smack into the WTC at high airspeeds. Their remains became part of a smouldering several stories tall building before that eventually crumbled into dust. I don't find it unreasonable that they were destroyed in the process
6) I don't find it unreasonable that someone could have stolen the recorders
7) While there remains a possibility that, out of a conspiracy, they did recover the recorders and have kept it secret, I also understand that:
8) They recovered the recorders from the other two flights, no? The NTSB also released the information on their findings. That accounts for 2/4 aircraft
9) On point 7, I ask myself, if it were a conspiracy, why hide just 2/4 sets of recorders? This potentially negates point 7
10) According to some fringe sources, there are claims that some workers may have found 3/4 recorders at the WTC by 2002 but were told to keep their mouth shut by FBI.
11) Point 10 may be a possibility, but it also raises the question to how they found 3/4 in one search and a few other questions that may require investigating
So, your question is, do I find it reasonable that none of the flight recorders were found? Maybe, maybe not. It certainly isn't out of the ball park for the flight recorders to be destroyed, but there is no conclusive evidence either. Not enough data. That's the way I look at it.