There are two big reasons you have trouble recalling a piece of information about your craft:

You use it so much that it is down to intuition, or you never use it at all.

For example, my relationship to Orders of Complexity has been reduced to sorting options in my head, and picking the first one that is simple enough to keep working, and fast enough to satisfy the current and estimated future scope of the problem (which is also intuitive Capacity Planning).

If you make me explain the decision it might sound like I picked one at random.