3 days steps missing after syncing with app

I am sorry you had the issue impacting a few days. Your watch maintains your history during the periods of time you cannot sync your daily wellness and/or saved activities. It is highly unusual that some days are altogether missing. If you are 100% certain you are using the same Garmin Connect email and you can still see the other data around the dates and going back for the time you have owned your watch, there will be nothing more you can do. The type of issue you just had though suggests an internal issue developing with your watch vs. the Connect Mobile APP. As soon as your watch syncs to your Connect Mobile APP, it is backed up in the cloud on your Connect web account so you will continue to see your prior synced data each time you switch phones or watches and continue using the same Connect account email.