Looks like you have deleted the whole track instead of just a segment (wrong button).

We’ve changed interface a bit to be clearer on this.

Lost track can be re-uploaded from the phone.

Currently, segment deletion does NOT lead to deletion of the corresponding track part. Track can only be deleted as a whole.

A segment just “highlights” an interesting part of a track and makes it playable.

In your case just narrow the segment so it doesn’t contain irrelevant parts.