Where is Track Me App?
It Is Disapperead from App on watch and Garmin Connect.
The "disappearing apps" issue is an occasional thing, but crops up regularly on this boards. It has happenned to me once. I don't think anyone has been able to replicate the problem consistently to identify the cause.
The simplest fix but most drastic is to do a master reset, and your missing apps will come back. Unfortunately this wipes your existing training data off the watch.
The less drastic, but more complicated fix is if you have a backup .FIT file of the relevant app, copy it over to the NEWFILES folder on your watching, and power it down then back up. This retains your existing data.