If the car runs, count yourself fortunate. You can check EVERY fuse, and you should. Many devices and modules have reverse-polarity protection that will blow fuses in such situations. Frankly, after 31 years in component-level electronic troubleshooting, I am surprised the car runs.

I believe there is an additional fuse on the back of hte radio head unit. Yank the head out (using the $3 tool you can get at WalMart) and check that fuse. If it is good and the fuses in the fuse panel are good, it is time for a new Radio. That is about a $150 solution and you will like what you get.