Well on many vehicles the fuse might not be running just one device and due to it being the 12 volt constant ignition switch feed may not even list the constant 12 volt radio feed fuse.
Basically you've two feeds one being a switchable 12 volt feed that usually has a fuse that is listed as a radio etc fuse but the 12 volt constant radio feed also comes off the ignition and since the ignition may supply other devices power the fuse may not be labelled as such.
Any factory installed stereo will have 2 fuses running the radio in the in vehicle fuse box but there could be a main fuse under the hood that feeds the inside fuse box its power so check those fuses too.
Best way to be sure that you've not blown other fuses is place the ignition into the run position , then use a voltage meter or 12 volt light test probe , ground the probe and then check each side of the fuses , both sides will have power if fuse is okay and if ignition is in the run position.But again you might find a fuse dead at both ends inside the vehicle , and if you do check under the hood bec another fuse or wire is faulty or blown etc.
Hope that helps and best of luck.
