how do I get my activity back if I delete it?

Did you see Post #1204852 marked as answer?

I had the same issue with my Garmin 1040. I have attached some of the files I found, maybe the more relevant (due to file size and date/time) is M7DN4100.FIT. Thanks.

File is downloadable here: https://www.dropbox.com/scl/fo/griihf9c8u6h52u662usz/ANj0EFi258StsOF4CTclG3c?rlkey=0lsqzd0gydtu9syjk46reoeov&st=kmyy27k2&dl=0

Hi, the battery went off during a race that was too long for the battery life. Trying t upload manually, but it says that the file is corrupt. Any way you can recover this one? I am really sad I lost this race. [solved]

Was this a multi-session activity? If so what were the distance/times supposed to be for T2 and run?

Yes, it was a triathlon. The swim was 3850m, 1:27:xx (when I looked at the watch coming up from the water), T1 some 400m walk, 16:xx (together with the swim1:43:57 from the race system), bike 206 km 7:52:46, T2 7:13, and the run until the watch died about 30km, I think. There was a run checkpoint at about 28km where the running time was 4:22 and the watch still had battery.

This will upload to Garmin - [solved]

However, T2 and run are combined. You can divide T2 using the edit function in Garmin Connect Web.

Dividing Leg 4 at 7:13 results in this:

Super! Many, many thanks!

this absolutely saved me today! thanks for the info. worked great