I tried solving the version the problem in which the codes are not necessarily unique, the grid is 1x36, only any character that appears in the code of any item that is a special today is marked, an item "appears to be available" iff all of the characters in its code are marked, and the customer chooses from the items that appear to be available for the first question.
It seems that this is not the correct interpretation of the problem statement.
The version of the problem in which all of the above is true except that the codes must be unique also appears to be the wrong interpretation of the problem statement. I'm sort of inclined to do something else with my time, since this seems to be more of a mind-reading challenge than a programming challenge.
It seems that this is not the correct interpretation of the problem statement.