retrojapan

I just got a Sony Minidisc recorder (MZ-N510) off of a friend today and immeadiately I popped in a minidisc that I recieved from another friend. I was listening for 2 hours before I put it into my bag. Later I went to listen again and got a message saying that the disc was blank. Thinking there was a problem with the player, I used the disc in my friends player and she got the same response. I don't understand how it can be a blanc disc because I didn't delete anything!! And the music was playing perfectly before. I'm really bummed out because the disc was sent to me from a friend who lives in Japan so it's impossible to get the music back. Can someone tell me what I can do? And where I can get the program to create other MD's because my friend lost hers. Thank-you!