What may have caused losing 5-30 of our two iPhone4's contacts without using iCloud or any other sync?

Question

My wife and I both recently discovered there was a select few of our contacts missing on our iPhone4. I think 5 or 6 from mine and over 30 from hers. This happened a day or so apart. Neither of us have done iCloud or synced with contacts or any of that. The contacts just went away. Starting a text and typing in the first few letters does not work for this. The contacts are gone.

What may have caused losing 5-30 of our two iPhone4's contacts without using iCloud or any other sync?

Answer 1

If you go into your Contacts app, select Groups in the top left corner and click on All Contacts -- do they show there? The phone only caches a certain amount of addresses and you may need to manually select lesser known Contacts if they get purged from the cache.