This is all just MHO- The problem is that your ISP (Spectrum, Charter, Xfinity, Starlink, hughesnet or whoever you use for the onramp) always knows when you're using the TOR and records the traffic. The ISP knows who and when, just not what or why. If the sender was in the US, the FBI will find out who sent it eventually.
The kidnappers would be wise not to communicate any further, because every time they do they are creating another fingerprint that can be used to pull their identifying information out of the billions of packets sent.