Mavic Mini - Going haywire into river - Link

So my buddy put his mavic mini up today for the first time this year, and he had it up for 2 minutes. This was the result.
No DJI Care, But it would not let us control it. We tried to bring it up and over and it would not do anything we tried.

So your buddy lost his drone and has no idea why.
No-one else will either from what you/he posted.
But something will have caused the incident.
If you/he wants to learn from the incident, a look at the recorded flight data is necessary.

To get to your flight data, go to: https://www.phantomhelp.com/LogViewer/Upload/
... where you'll find instructions to upload the data to that site and it will give a report
For help interpreting the data you can post a link for the report here.
Or just post the .txt file.

Hi there. Thank you for reaching out. We're sorry for the unpleasant experience. In this kind of situation, we strongly suggest contacting our team at https://www.dji.com/support by sending them an email for further assistance. Again, we're sorry for your loss. Thank you for your valued support.