Clearly you will never see these materials when asking users to come to you for more formal lab research. They are also the types of things that users will not think to mention because they may not recognize that they had to create them because of a flaw in the tool they were trying to use.
Often users will not realize that they behave in a certain way within their own environment. By observing this natural behavior yourself you can get some fantastic insights into the reality of how something is being used and how you can enhance its design to make it easier to use.