Garageband missing audio files are not in the media folder

Hi, I've tried to listen to some garageband songs I created about 3 years ago. The projects are there but the audio files are not. They audio files are not showing when I open the project in garageband. I've followed the online advice saying to go to the project and selecting 'show package contents', and then go to the media folder. I found 2 .aif files but there should have been loads. I've searched my iMac for .aif files but it can't find the missings ones. Where could they have gone? They have disappeared out of the folders it seems and into thin air. Any help would be greatly appreciated.

Thanks.