hi srchadwi, somehow I have no way to reply your PM, maybe I'm still too new on the board?
anyway, I didn't discuss much with the shop about the prop coming off. at the time I thought maybe I didn't put the prop on properly before taking off. the prop went missing after the crash and I couldn't find it after searching the area for an hour. my attention was on the motors as there were sands inside after the crash and once I was home I opened it up to clean and found one of the motors stuttering. I was going to the shop to get a new motor when they told me it's more likely to be the ESC. I was still thinking the crash had caused the problem rather than the other way around. The next day they called me and said they found the problem to be the ESC and they had replaced it for me. When I picked up my quad I did ask if the ESC could had caused the prop to fly off and they just said "maybe...". They were quite busy at the time so I didn't ask much more.
Then I searched on forums (both DJI's and here) and found a few similar cases then I realised it could have been the ESC's failure to cause the motor to stop or reverse and making the prop to fly off. In one of the posts I read the OP also couldn't locate the prop afterwards. Can the prop be broken into pieces in such situation?
Again knowing now that a ESC can fail at any moment without prior warning and lead to a crash I just hesitate to fly comfortably. On the day it happened to me it was on my 3rd battery and I did not have any crash during the day. I did come very close to a waterfall because the wall had probably blocked the GPS signals and it was drifting. I didn't notice until it came very close to the waterfall but was able to correct before hitting the wall. Not sure if water could have creeped into the hull and damaged the ESC in the process.
Here's the video I made about that day's flight and at the end I included both the close call to the waterfall and the final crash:
https://www.youtube.com/watch?v=IO4XZOx2IEE