I am using an example. If John was saved in my contact list and I delete his name would it still be in the phones memory. If I open the messages and start typing John, his name and tel still appears. Please explain how this is possible?
My particular field of expertise is iOS Jailbreaking and Unlocking.
It's like a hard drive. The data isn't 'entirely removed' unless the part of storage that it's taken up is written over or the cache is emptied. Chances are, you still have some messages or calls with him in your device, until it's all deleted, you'll still see the name and info cached on your device.