In reality, they need to get the hardware back as soon as possible because that is a big footstep trace to where they are. the codes will tell where datas are stored and sent. If they are clever enough to erase every data after being sent in real time, there is still the "firmware" that runs the device itself that can obviously be sniffed , traced and reverse engineered to know what exactly it is doing.
If they can code their device to destroy it physically after the data has been sent, then that's the end of us! haha no trace at all.