Can I use this card to search for cards like Isengard Messenger or Mirkwood Pioneer? Or does it only work with Saruman and the few events?

I would think that the cards with an optional doomed price does not qualify as having the doomed keyword, both for the wording ("you may give doomed" seems to imply that they don't have it unless you choose that option) and also for a question of card anatomy (usually keywords are always printed in a separate line above the rest of the text)

You can only search for cards with the doomed keyword, not that reference doomed in their text.

Well that's sad. Thanks for the help guys!