Whitis and MaxHeadRoom are both correct. What they have not spelled out but that you may care about, is that switching power supplies operate in the many-kilohertz range or even higher.
A switching power supply definitely can create interference in nearby electronics, but the ferrite suppressor will have no measurable effect on the device you are powering, since it effectively absorbs or damps out only high frequencies. The further it is from the source of the high frequency (the power supply) the more of your power cord is available to act as an antenna and radiate interference. If you're curious and have time to kill, you might put a small radio near the power cord before and after you re-install the suppressor.
Virtually all power supplies for electronic equipment these days are switched mode supplies - they can have efficiencies up in the 90%s, much much better than older linear designs. It's also possible that it was intended to zap interference generated by the scanner, since the digital circuitry in that would also run at high frequencies.
"A machinist's (WHAP!) best friend (WHAP! WHAP!) is his hammer. (WHAP!)" - Fred Tanner, foreman, Lunenburg Foundry and Engineering machine shop, circa 1979