Thank you for letting us know who they are... I wasn't sure before now.
A comparison between two things, typically for the purpose of explanation or clarification.
RC vehicle = Line of sight realtime control, loss/interruption of signal tends to have vehicle out of control.
Mars Rover = Send short controlled movements to vehicle that will not run away when out of communication with controller.
I would have thought this was common sense and not an issue to blow a gasket over, but then it has been over 50 posts where others have tried to help, but stubbornness prevails.
There is NO easy code or solution... that is my entire point! A proper, functional fail-safe for a moving object controlled remotely will depend entirely on your infrastructure, robot style, control methodology and coding skills.
Stop asking for easy!! Make some actual attempts and show us some actual code that you have written and then maybe we can help.