Can you import a .15 file back into audacity?

I exported my class’ podcast and selected mp3 thinking that it would automatically convert my file from .aup to mp3. I then learnt that I needed to install some ‘LAME’ files and so what resulted was a .15 file on my desktop.
I merrily carried on and uploaded it to our school website. I tested it in Firefox and although a message appeared it still played using using windows media player? So then just to test fully I tried it in Google chrome & Internet explorer and I received an error message, which I now believe is because the mp3 file is unsupported if I hadn’t installed the lames.
Then, to top it all off I thought it would be a good idea to tidy up my flashdrive and in doing so I deleted the audacity data files associated with my final edited podcast.
I tried to recover this data but to no avail.
So, the only hope I have now is if I can import my .15 file that plays in Firefox back into Audacity and then export again to the most recommeded file extension to be used across all browsers plus Apple devices and Android tablets. I know if I publish as it is I will get loads of grief saying it doesn’t work. Which will be true because as far as I can see it will only work in Firefox.
HELP!!! Or in the words of Bart Simpson, Doh!!!
Thanks from someone who is feeling very stupid right now,

Windows? Which one? Which Audacity?

Audacity will not let you export Something Else if you’re missing the lame software. It should just say “I can’t find lame, do something else.”

Since you’re on Windows you may not know what kind of file you actually have because Windows aggressively hides the filename extensions. So there’s two problems. I don’t know of a .15 sound file type.

If you can get anything to play it, I suppose you can capture it as if it were a YouTube video sound track. That would work.