Lost the key and a P1000 code?

The P1000 code isn't the reason you cannot communicate with the vehicle, there is something else blocking it. P1000 is simply saying that not all monitors have been run. So something like EVAP or O2 sensor testing hasn't occurred and still needs to run. It will come up as a code if someone goes in and erases other codes as it resets the modules and erases any learned info. That also shouldn't block key generation if the proper tools are used. I suspect you will need to use a NGS scan tool or equivalent aftermarket tool to enter the system and see what codes are stored in the security system that may be blocking the keys. What scan tool are you currently using?