Lost track on export

Hi there , I have been working on a song and exported it as an MP3…it worked fine on playback on audacity and also on my phone as an mp3…I then went back and added a drum beat track (recorded using a microphone pointed towards kit). This was fine on audacity playback , but after I exported it , it completely disappeared on the mp3? I have tried three times now and it just wont register it? what am i doing wrong please?

Which version of Audacity?

There is a known bug in a couple of old versions that can cause a project to lose its audio if you overwrite the project using the “Save Project As” command. More information here: https://forum.audacityteam.org/t/important-bug-fix/48358/1

The bug is fixed in the current version of Audacity, which is available via the Audacity website: https://www.audacityteam.org/download/