Nan took the Mini down to Scottsdale Mini on Wednesday to deal with a check engine light that wouldn't go away. While there she asked the service folks about the sound. They said that what she heard wasn't the window or the locks, rather it was the fuel pump cycling. It only does this when the vehicle has been shut down for 15 minutes or longer and it is a soft enough and high enough pitched sound that most people don't hear it.
That explains why I can't hear it. Between flying around in the back of C-130s and C-123s without hearing protection for 4 years and riding scoots of various displacements and styles without ear plugs, I've lost significant hearing range, so this is a sound I'll just never hear.
Thanks for the input.