Some groups are not visible in my WhatsApp I am not able to see some of the groups for which I am a member. My name appears in the group admin's phone. But he is also not able to remove my name and add it again. Other group members cannot see my name in the group member list. So I don't know exactly what the real problem is. I have uninstalled WhatsApp and re-installed it, but the problem remains the same. (Still I cannot see some of the groups in my phone).
Can you please find some way to come out of this?
Try the following steps:


Make sure that admin user have your  phone number in your address book.
Ensure that admin user is using WhatsApp Messenger.
Make sure that admin user have the latest version of WhatsApp. 
In admin users Android phone book, make sure that all contact accounts (i.e. SIM, Google, Phone) are "visible" or "viewable".
In your Android phone book, ensure that all contact groups (i.e. Friends, Family) are "visible" or "viewable".
You can make your contacts "not visible" and then "visible" to force a refresh. After doing this launch WhatsApp > > Menu Button > Refresh.    
Alternatively, you can use all your contacts, not just the "visible" ones. To do this go to Menu Button > Settings > Contacts > Show all contacts.