I've been working on a physical Escape Room and it's important to me that the game have a strong narrative. There needs to be a good, contextual reason why the clues exist in the way they do. So I've been trying to think of a unique explanation for it.  

When you break it down to the most abstract, an Escape Room is simply a room where the needed information (the "code") to escape ("unlock") is obscured for some reason.  But why?  Here are the categories I've found:

1) The Information Meant to be Hidden From Most but Discoverable for a Select Group:  Why isn't the code to a combination lock simply written on plain paper?  Because whoever created the lock doesn't want everyone to know.  Then why is there a clue to learning the combination? Because whoever created the lock wants a select group to discover it.  This is the most common abstract narrative for an Escape Room.  Examples include, finding the combination to a bank safe (bankers need the code, everyone else shouldn't know it). Escaping from a prison cell using someone else's escape plan (original escaper created and needed the code, prison guards can't know it).  Entering a forbidden tomb (maybe only those "worthy" enough to solve the puzzles can unlock the code)

2) The Information is Available to All but Accidentally Obscured:  Here, the "code" to the "combination" is not meant to be hidden by whoever created it, but it is accidentally hidden due to some other factor.  Perhaps the person behind the lock is an alien who simply speaks another language.  Or maybe some unforeseen act of nature hid the information and the players must put it back together.

3)  The Information Is Available but Was Never Deemed Relevant:  An example would be if you are trying to find the location that someone went to, and while this information isn't necessarily secret, it isn't immediately accessible.  Players would have to comb through documents, like a travel planner, to learn this "code".

4)  The Informer Cannot Easily Communicate The Code:  In this category, the person behind the lock wants to give the players the information but cannot due to communication problems.  For example, they call the players on the phone but are only able to give out a fraction of information due to static.  Or the informer is a ghost and cannot speak directly to the players and can only communicate to the physical world through the clues (by the way, this is the narrative I'm leaning towards!)

So I'm wondering if anyone can think of any other categories not listed here or can come up with some great examples of each.  I believe most escape rooms fall under the first category but I haven't actually been to that many so I don't have a lot of examples to go on.