E93 iDrive Display Question.

I have a 2010 328i Convertible with iDrive. I also have a Verizon Motorola V3m (RAZR) phone paired to this car, which works fine.

Recently, I noticed that, in addition to the signal-strength meter displayed at the top right on the iDrive display screen, there was an icon immediatly to the left of the signal-strength meter that I will describe as a old-time phone receiver with a diagonal line through it.

If I used the system to make a call, the icon remained, but the diagonal line disappeared while the call was in progress, and returned after I ended the call.

This situation remained for a few days, and then reverted back to showing only the signal-strength indication on the iDrive display, It hasn't returned since that one episode.

I have scanned the owner's manual, and can only find a brief description and picture on page 19 that describes the signal-strength indicator. The manual mentions that the display will also show some sort of indication for an incoming, outgoing or missed call or a SMS/text message received.

Its not a problem, but I am curious why the icon appeared and then disappeared in what I think was a random manner. It seems obvious what the transient icon represents, but why isn't it consistent? I have made ZERO modifications to the phone or the pairing of it to the car.

Anyone have any ideas?