Mp3 not showing in library
If it doesn't turn up in the library even after a reboot (which should definitely have triggered the media scanner to add it to the library), the only reason I can think of is some .nomedia file being in the path. You can try to analyze that (finding whether there is one), or...

There are media players not using the library, mainly for FolderPlay &amp; AudioBooks. Using one of those, you can navigate to that folder from within the app, and play the files. If that doesn't work either, the files might be corrupted or using an unsupported format.