Hello, my name is ***** ***** I'll be assisting you this evening.
I know that you are probably BEYOND frustrated with this, and I am sorry someone stole your tablet. I may have you go through steps you have already been through, please bear with me and repeat them. Sometimes we miss tiny details that mean a lot. Just follow these EXACTLY.
1.) Turn the tablet off. Then, press and hold the POWER BUTTON until the "Device Option" menu appears.
2. ) Choose POWER OFF and then OK.
3.) Press and hold the BACK button and POWER button at the same time for around 10 seconds.
4.) When you see the Android and warning triangle, press BACK once.
5.) You SHOULD see the Android Recovery screen now. The HOME/MENU button will allow you to navigate.
6.) Use the HOME/MENU button to navigate to WIPE DATA/FACTORY RESET. Press the BACK button.
7.) On the next screen, choose "YES - DELETE ALL DATA" and press the BACK button.
8.) On the next screen, choose "REBOOT SYSTEM NOW" and press the BACK button.
It should come back up after this. This is the correct way to master reset the Coby Kyros tablet. I have also included a video for your reference. CLICK HERE FOR THAT.
Let me know if that didn't work and I'll research to see if there is another way.
If this DID work, please rate my answer with 5 stars so that I may receive credit for assisting you, as this is how we are compensated.