Stop thinking about X, lets move on to Y

So yesterday I went to the used disc store and bought the Oasis single “Supersonic”. Instead, the disc for “Shakermaker” was in it instead, no biggie, I thought I could just return it or whatever. Then I put the disc in and it had 2 extra songs “I Will Believe” and “Cloudburst”, which are from the Supersonic single. Anyways, I can’t find anything that says that the single is supposed to have those songs, so does anyone know if I have an error disc or something of the sort?  ?