The red wire comes straight from the battery,alternator, regulator junction. The only way you could lose power there is for the battery to have a bad cable connection or the fusible link that goes to the right fender junction to blow. Unless the connection at the fender junction is bad going to the Bat, alt reg junction.
Here is how the wires run. From the battery fender junction.
The red wire going to the right of the junction is the feed wire for the cab. It goes through the firewall block and forms a junction with three other wires shown here. Don't pay any attention to the arrows, they are for other problems.
One of these red wires feeds the horn relay, one goes to the key switch for key on power, and one goes down to the fuse panel to feed the key off orange wire power, and the last one is the one which feeds the headlight switch. These are shown here.
Do you have power anywhere. Horn, ignition, turn signals, hazards, etc?