Does any of you have a simple way of restoring iPhone contacts?

I have recently noticed that several of my contacts, one of them used just a few weeks ago, have vanished from my iPhone. They are still there under Messages (if I start to compose a new message to a contact I messaged before), but restoring contacts from messages is a rather slow cumbersome process.

So if yo have a simple process for restoring lost contacts in one fell swoop, I would like to hear about it.