How can I know if a contact has uninstalled WhatsApp?
There is difference between UNINSTALLING WhatsApp and DELETING WhatsApp account.If the contact has just simply UNINSTALLED WhatsApp, the contact will still show up on your device with everything (Display Picture, About(The Old Text based Status), Last Seen) intact (Of course depending on their privacy settings they had before uninstalling it). The only thing is that messages will not get delivered now and also the last seen, if visible, would be showing a few days ago (In today’s world, such last seen are almost inexistent.Everyone checks into their WhatsApp atleast once a day).If the contact has DELETED their WhatsApp account, regardless of whether they have uninstalled the application itself or not, the contact won’t be visible in your contact list anymore until they register for WhatsApp again using the same number.