This whole koan guessing game is a bit silly. The whole point of koans is that it takes long months of meditation and a very special frame of mind to understand them. If a guy reading a blog could guess the answer after five minutes' thought, the koan wouldn't be worthwhile anyway (I am willing to grant Eliezer his fox koan, but even he only solved part of that one, and only with the help of centuries of Western philosophy and deep personal knowledge of the issues involved).
But I will hazard a guess as to Annoyance's interpretation. Annoyance wants us to consider mundane experience more. The monk was hoping Joshu would teach him something really exciting about Buddha or enlightenment or meditation. Instead, Joshu reminded him that after you eat, you've got to do the dishes. The monk realized that Zen wasn't about fancy theories of ultimate holy reality, but about living mundane experience as fully as possible. He also realized that his thoughts of enlightenment were distracting him from a task he should be carrying out with his full mind, and when he concentrated his full mind on the present moment, he achieved enlightenment.
It takes only a moment to find the right answer.
It takes a lifetime of struggle to know where to look for it.
Given a map and a flashlight, how long should it take?
Joshu Washes the Bowl
A monk told Joshu: `I have just entered the monastery. Please teach me.'
Joshu asked: `Have you eaten your rice porridge?'
The monk replied: `I have eaten.'
Joshu said: `Then you had better wash your bowl.'
At that moment the monk was enlightened.
Mumon's Comment: Joshu is the man who opens his mouth and shows his heart. I doubt if this monk really saw Joshu's heart. I hope he did not mistake the bell for a pitcher.
It is too clear and so it is hard to see.
A dunce once searched for fire with a lighted lantern.
Had he known what fire was,
He could have cooked his rice much sooner.