I have a 2009 F 250 5.4L, couple days ago it acted as if the alternator had gone out and killed the battery. I swapped batteries with a coworker to get the truck home and when I hooked the battery back up, the battery and the alternator both tested fine. I've put the voltmeter on periodically and everything seems to be fine and all electronics are working except for the radio. I did a light test on the fuse and it showed a bad fuse so I tested the fuse and it tested fine and I put a new fuse in and tried the light test again and it failed. Any idea what the problem could be? Any help is greatly appreciated

 

I thought there might have been a bad relay since there is no power to the radio fuse. Tested all relays with no success. Any thoughts would be helpful