I was just making a single character change to my best money making ad in my best campaign. I thought I was creating a new ad, but accidentally edited the old one.If you edit an ad at all, it deletes the ad and replaces it with the edited version. This new edited ad has lost all it’s account history which is part of the Adwords auction quality score and has an impact on how that ad will be served in the future.  If it was a real winner, you may really notice the difference in CPC, ad position, or targeting if using conversion optimizer. Deleting an Adwords ad is irreversible if you are using the web interface.

If you have accidentally deleted a productive ad you may think all hope is lost and that you have to start over with an exact replica. Not so my young padawan.  Open up Adwords Editor and:
1. Get Recent changes (top left button) basic is fine
2. Click on the folder for the campaign and subfolder for the adgroup in question. (on the left)
3. Click on the tab that says “text ads”
4. Sort by clicking ’status’ at the top of that column (optional)
5. Find your deleted ad and click anywhere on the horizontal row. The text will have a line through it.
6. Look at the bottom section and make sure you have the right ad selected.
7. At the bottom right change the status dropdown from ‘deleted’ to ‘active’.
8. At the top click on ‘Post changes’

9. That’s it! You can check your web interface, and your ad will be there in all it’s glory with all of it’s important history intact. Feel free to buy me a beer next time you see me.

EDIT: Here is a screenshot.