There is a technical discussion taking place at Google Groups on the topic of bringing back to life a deleted keyword from Google AdWords.

Jeff Posnick from the Google AdWords API Team said he isn’t aware of a way to retrieve deleted keywords with the API. He said, this is a feature request:

But the conversation has not stopped there. AdWords API users seem to be figuring out some methods to kind of reverse engineer some of the API reporting tools to come up with a way to get those deleted keywords. Personally, I am not a heavy AdWords API user, so I don’t know if any of those methods would work. If you know of a way, join the conversation and share.

Forum discussion at Google Groups.