"The prisoners have not been found yet."
Translation:wej qama'pu' luSamlu'ta'.
The original Klingon sentence for this exercise is wej qama'pu' luSamlu'ta'.
I see that in the English-to-Klingon direction, it can also expect tu' -- while that verb does mean "discover, find, observe, notice", using only Sam in the default answer is probably better.
I'll edit it and "demote" the readings with tu' to accepted but non-default translations.