Whatsapp icon missing
my Whatsapp icon is missing in the phone. at first, I thought I had accidentally deleted it. but when I went to the App Store to try download it again, I couldn't as it showed 'open'. so I assume that's because the app is still in the phone ? but I can't open the app either. so I can't delete it & download it again because it's missing from the screen. how do I get it back ? or is there any other way for me to delete the Whatsapp app & download it again? please help. I desperately need Whatsapp again. thank you.
iPhone 4S, iOS 7