Was this in a radio station (or was someone nearby acting as a radio operator, like a police station or dispatch center), by chance? Or maybe in a lab setting where they may have gear that is affected by interference? They tend to be picky about RF interference, and Ethernet can be fairly noisy on certain RF bands. In that case, the ferrite bead was likely to do the exact opposite; They wanted to stop the Ethernet cables from acting as an antenna and broadcasting RF interference.