"You fried the final," he said. Antenna the culprit?

Cobra 29LXT, tweaked three months ago and was fine, I thought. Honestly I use the radio so seldom( always on with volume up just enough to hear if someone calls me) so I don't know if this just happened last week when I took delivery of a 2015 Prostar, or if it was already burned up.

But anyway I took said radio in to have it looked at this morning and the tech tells me I fried the final. Even showed me the one that supposedly came out of my radio. Yep, it melted alright. He said I should have smelled it when it happened.

He suggested it is a problem with or short in the factory antenna. So my question is what do you think of this diagnosis and where do I begin to look for the problem?

To prove that yes, indeed I am stupid, I plugged it in once I was back in the truck (AMA-against medical advice) and just as he said would happen I think I fried it again. The radio ain't gettin out. Needle doesn't even move. I shoulda' listened but it being a brand new truck I didn't believe him, so being stupid cost me 33bucks.
Thanks for your help.

 

Yeah, that makes way too much sense, should have done that. I simply Unplugged, then replugged. There is a 5amp in line fuse. Seems that should have blown.