Does Time Machine erase everything on your hard drive?

[defaultxkr7hbp01k1r]

And if it does is there a way to get it back. I shot a short film and put it on my external drive. Before editing, I backed up my computer with Time Machine. Next thing I know the footage is gone. Any suggestions? 

[Peru Bob]

Gone from where?

Is the external drive connected?

Do you have a backup of the media?

[defaultxkr7hbp01k1r]

External drive. I do not have a backup of the media.

[Peru Bob]

Are you sure that you saved it there?

[defaultxkr7hbp01k1r]

Yes, I'm sure. 

[Ann Bens]

External drive. I do not have a backup of the media.

By @defaultxkr7hbp01k1r

FAQ: When to use "Save A Copy," or "Save As," or just "Save".

[Jeff Bellune]

The only way Time Machine should erase anything on your system is if you restore something. If all you did was back up using TM, then nothing should have changed on your system at all. Time Machine will delete old backups if there's not enough space on your selected backup disk, but it won't delete data or apps.

What do your TM preferences look like? What disk did you choose to backup to?