As someone else said, it is indeed upon the video. I remember its existence distinctly because in the early days, it also kept kicking off obsessive discussion about whether or not Brian was “lying’ when he said he did not have a cell phone, but then pulled his own out of his pocket (for the record, I opted for ‘an individual’s personal verbal lexicon’ explaining the difference, wherein Brian’s cell phone was so retro and inferior that in his mind he disdains it as being a ‘real’ cell phone).
As I recall, there is some sequence of events on the tape that results in one of the officers asking Brian to go get Gabby’s phone and bring it back to him, after which point Brian takes off with the keys.
In my mind, I thought this meant that Brian had taken Gabby’s own phone and tossed it into a center console between the two front seats or similar and was leaning on it or something, thus barring her from getting it.