Cheapest priced copy (Worldwake): $16.99 at Card Kingdom, near mint, their price list as of .
Carol Marcus, Scientist Sleuth 
Thada Adel, Acquisitor
Legendary Creature — Merfolk Rogue · 2/2 · Mythic · Stardates · #5
Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
Whenever Thada Adel deals combat damage to a player, search that player's library for an artifact card and exile it. Then that player shuffles. Until end of turn, you may play that card.
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
2 printings · $16.99 to $34.99 at Card Kingdom
3 rulings from Wizards of the Coast
- 1 March 2010The exiled card is played using the normal timing rules for an artifact, as well as any other applicable restrictions. For example, you can't play the card during your combat phase unless it has flash. Similarly, if the exiled card is an artifact land, you can't play it if you've already played a land that turn. If it's a nonland card, you'll have to pay its mana cost. The only thing that's different is you're playing it from the exile zone.
- 1 March 2010If you don't play the card before the turn ends, it simply remains exiled.
- 1 March 2010When the triggered ability resolves, you must search that player's library (and they must shuffle it) even if there are no artifact cards in it or you choose not to find one.