You may see this issue on the Add Single / Add Multiple volunteers function by clicking the First Time Volunteer link, click here string.

You may have entered Volunteer information in the added individual/multiple volunteer screen. But if your mobile/tablet screen gets locked before the data is saved,  the contact information does not get Saved. So when you unlock the screen, you dont see the volunteer information you had previously entered.

If you are entering new volunteer information, please make sure that the Sleep Time on your mobile device is set to a higher value, so that it does not lock automatically when you are entering data. Also, make sure that the data is saved before the mobile/tablet screen is locked.