Occasionally syncing issues can cause workouts to sync to the app without some amount of relevant information including heart rate samples or GPS maps.
Generally the missing data can be easily restore to the workout by re-importing it into the app. To re-import the workout open the app on your phone and tap WORKOUTS>(+)>IMPORT FROM APPLE HEALTH. This re-imported workout should have complete workout data.
If re-importing the workout does not restore your data please contact firstname.lastname@example.org so that we can look into this issue further.