The teleporter stones get replaced on act change with another set, and should end up in the hero's inventory. Were you perhaps completely loaded with loot, and couldn't take another 10 weight (assuming the DK was carrying them in act 2)?
In any case, you can replace them (
Inventory files), though they disappear entering act 4, so it doesn't sound like you would have them for long.
Did you talk to all of the Raanaar? There is a specific one you need to talk to to complete the quest (they should then walk away in a cut scene).