There are plenty of people in this forum asking about how to recover accidentally deleted activities....so many, in fact, that it is clear this is a design flaw with the Vivoactive 3. I had this happen to me today on an "epic" run. It's SO INCREDIBLY FRUSTRATING.
Can you please update the watch such that you need to do something more than just touch the 'DISCARD' section of the screen (which is sensitive to sweat, rain drops, etc.)? Maybe hold down the side button for 3 seconds or something?
Sincerely -
A very frustrated runner