My 2003 ford focus lost all power going 50 down the road. Lights worked, dash lights worked but nothing happens when I turn the key. Tried replacing the ECM because thats what the shop reccomended. Had a guy come out to reflash it for me after I bought and installed the new ECM. The guy that came out to do that said it wasnt the ECM and maybe a ground wire. It also had a blown relay but thats been replaced as well.

 

We don't like to poo poo somebody's theory, but unless everything else is checked and confirmed functioning correctly ,automatically condemn the ECM.
The gent that suggested a possible ground wire should have a better idea of what is going on. Unless and until you can verify all connections are good and clean, that is where you will have to start. We could be losing either power or ground and until we check , it could be either one of them.