That's why you hire ex-FBI guys to work your security. Even if its not kosher, they can get a look at things most people cannot. You should read that Big Lead piece describing Lester Munson talking to Dan LeBatard.
In answer to your previous question, police records are largely public and while you are not going to be able to get all the material of an ongoing investigation, like reporters, the NFL Security guys at least will be able to get a heads up about what is involved, even if they don't get the evidence handed to them in a bag. Your employer could eventually see it, just not as fast as NFL security.
http://thebiglead.com/2014/09/10/esp...-it-for-years/
As for my theory, the best bet is that NFL Security had the tape, watched it and summarized it for Roger and Co. No one spoke about HAVING the tape, only being aware of the contents because its release wasn't authorized. They made a judgement it would not hurt Rice more and told the execs so. In this case, they were wrong.