CIA confirmed: no bombers on 25 March 1948 

As you can see from "Air Information Report" from August, they were very aware of aircraft movement. Manufacturing informational awareness was also high on their list of priorities.

According to this report, the CIA was aware of bomber training missions from Moscow to Vladivostok and back again on 13 and 14 March, and then on 15 and 16 March. Nothing for 25 March...or even the 23rd or 24th.