So this happened a few days ago. I can still get into the storage area, but the missing button looks awful.
BMW wanted over $300 to replace this button, so I will buy the part (hopefully from a breaker/junkyard donor car) and install it myself. I still have a bad taste in my mouth from the price I paid for the changing of my roof hydraulic pump, and the British show Wheeler Dealers (in reruns) has me itching to turn some "spanners."
edit: While my search turned up nothing on point, by browsing I found the DIY "how to's" on this issue under Board index ‹ E85 / E86 Z4 Discussion (2003 - 2009) ‹ How-To ‹ Interior. Now if I could just find directions on removing the other parts of the interior rear bulkhead, I could swap out my driver's side cracked bulkhead panel at the same time.