I sent a mail to the Service Center e-mail address. They told me thatI returned to a badly dented door and found that the thumb drive had filled the day before so Sentry mode had stopped recording. I contacted Tesla via customer support chat (the only way I could get someone to help) and was told in no uncertain terms customers cannot get copies of the uploaded video. Please let me (and us all!) know where you called and how you were able to get your video from Tesla. I have a large insurance deductible and even larger sense of satisfaction riding on it! TIA!
a) you need to enable "data sharing" in the menu in your car for images to be sent over LTE (can't remember for the moment where exactly this is, but when enabling sentry mode for the first time a screen also popped up; that screen did explain tat "data sharing" would in certain circumstances upload backup copies).
b) except if Tesla sees something that they need to investigate (to enhance Sentry Mode) the images are only kept 72 hours.
c) there were no guarantees
24 hours later they sent me a video of the left B-pillar camera of the incident (someone shattering my side window).
Mind you, things like this could be different in different countries.