Hi Natasha,
First of all, I'd like to assure you that forms are either successfully sent to the server or remain safely on the phone. Forms remain on the phone until the server notifies the phone that the forms were successfully received - this is how we ensure forms cannot get lost in the middle.
Secondly, your mobile workers can see the status of their forms on the mobile application itself. The app displays the number of unsent forms that remain on the phone.
On Android phones, the number of unsent forms is displayed on the "Sync" button of the home screen. Under the sync button, a notification is displayed whenever forms have been successfully sent to the server.
On Java phones, the number of unsent forms is displayed on the "Send all unsent" menu item, or if the app is in Sense mode, it is displayed on the top bar of the phone.
If you are concerned that forms may accumulate on the phone, you can set an "Unsent form limit" for your application. If an application exceeds that limit of unsent forms, the phone will highlight the unsent forms message in red to make the issue more apparent. Read more about configuring this limit and other application settings here:
https://help.commcarehq.org/display/commcarepublic/Application+Settings
Sorry if we are overwhelming you with information, and thanks for reaching out!
Amelia