Restore file as it waqs before noise reduction

Hi everybody,
I recorded a file in a classroom, but there was a lot of noise.
I removed the noise using the tool provided by audacity.
But, I realized that this noise reduction was not properly done.
Now, I need to restore the file as it was at the begining to do it again with better knowledge.
In my directories, aside the audacity file (20170131.aup) I have a directory (20170131_data).
Is it possible to restore this file as it was before?

If the project has not been closed since making the changes, use “Undo” (Ctrl+Z or Command+Z on Mac) to step back through the Undo History.
If the project has been closed, then it is not possible to undo the Noise Reduction effect and you will need to go back to an earlier backup version of the recording.
(My crystal ball tells me that you didn’t make a backup of the recording before you started work on it, in which case you have learned the value of backups).