You can use the tag in the music option for this. Whenever you play music, it gives you the option to place a tag to it. Than you could just use the tag to check if the music is playing.
For example: Let's say your Music is titled "Music1", you can place in the tag section "Music1"
Audio, If tag "Music1" is not playing (you need to select the playing tag and invert it)
.....Audio Stop All
.....Audio play Music1 lopping at volume -0db (tag "Music1"
This way it detects if there is no music playing (first time) it will play the music, than each time you go back, since the music is still playing, it will not restart the music.