Somebody wanted a day off and decide to pull the fire alarm. In modern times this means using a VPN internet connection to phone in a bomb threat.
Should be untraceable, but what do I know. I still own a Commodore 64.
Nothing is untraceable to the feds.......
The VPN provider would be served with a warrant and they would provide the originating IP and MAC they masked.....Even bouncing off several VPNs would only slow them down maybe 24 hours...