Yes it was a real bugger. I had 1,3,5 after 2 guesses and in retrospect there are at least 25 possible common words with those 3. In actuallity you could have got 1,2,3,5 on your first go and still not get it if you employed the single letter change as there are 7 possibilities. In that case a better tactic would be to burn a couple of guesses that used all the possible 4th letters.
It also goes to show the 'luck' of the first guess. I worked it out if THINK had been my first word I would have got it in 2 or 3. How ironic!