More interesting to me is the fact that many people with absolute pitch start to lose it in their 40s and 50s. This has happened to me too. What happens is that your pitch assessment often starts going sharp, so what you thought was a C was actually a B, say. For me the pitch assessment accuracy differs depending on the harmonic content of the sound: guitars and harmonicas are awful, but pianos and flutes etc. seem to do better.

It's a very frustrating and difficult to explain phenomenon. I hate to use the oft-used but inaccurate color analogy, but it might be valid in this context. Imagine that everyone around you is fully color-blind, but not yourself. People are amazed that you can tell something is blue just by looking at it. You've had this ability your whole life. But then one day you look at something and report that it's blue, and someone uses their color-analyzer and tells you that it's not blue, it's in fact yellow. And they're right! But it still looks BLUE to you. Something has broken, and you can't explain it to others easily because they can only see gray.