Or as Kirk said in The Immunity Syndrome,"Insufficient data is not sufficient, Mr. Spock. You're the science officer, you're supposed to have sufficient data all the time".
The useless "I don't know" should really have been replaced by "Here are my X best guesses, Captain, each accompanied by the specific bit of missing information that will make or break the hypotheses. You can choose which missing bit or bits to pursue, in which order", with the value of X depending on how much of a hurry the heroes really are in...
That'd give Kirk something to chew on, as well as insert extra scifi intrigue into the episode - say, three exotic scenarios at the price of one!