Today's disconcerting experience at work: discovering a hole in my memory.
I've spent a bunch of time over the last day or two trying to get up to speed on a subtle and complex area of networking protocols. The relevant RFCs are cryptic at best; the text covering a variety of complicated deployments is compressed to a mere couple of pages.
Eventually it occurred to me that there might be some internal company documents about the area, and I went a-hunting. A few searches later I'd found a much more helpful 30 page internal document, with detailed explanation, examples, multiple colours, diagrams, the whole works—very useful and much clearer than the standards documents.
So it was a bit of a surprise when I got to the back of the document and found the revision history page: I wrote the whole thing. It was only four years ago and I don't remember anything about it.