Contrary to popular belief, K4 is not a one-time-pad cipher

One Time Pad

Besides the fact that K4 is “apparently” unsolvable, there is little to no reason for believing this is the cipher method they used.  James Sanborn and Edward Scheidt said K4 would be hard but they never said it would be impossible.

And if an OTP cipher was used correctly, K4 would be impossible to solve.

Might as well just give up now.

Seems rather pointless for them to use it and for us to consider it likely that they would have used it.