There is a finite, calculable probability that he will be found outside the gates of the prison walls. For large objects like prisoners, you would have to wait longer than the lifetime of the universe for this miraculous event to happen.
I've wrestled with the Uncertainty Principle for years now and it still doesn't fully convince me. The issue isn't simply that you don't know the location of the particle. It is also that you've made an imaginary assuption that the container is absolutely solid, static, and impenetrable. If it is in reality none nof those things, if you simply lack the ability to see the holes, then escape is neither surprising nor a grand principle.
