Insurance and Apple Care Plus are two different things. Insurance covers certain things, and Apple Care Plus is an extension of the original warranty on the phone. Many insurance plans cover things that the warranty and Apple Care Plus do not cover, such as loss or theft. The iPhone warranty and Apple Care Plus do not cover those things. Apple does not offer insurance on the iPhone. There are a number of 3rd party choices for insurance, and ones through many of the the cellular carriers. Be careful if you choose one of them.
Insurance will not get your lost phone, but it can replace it, usually with some type of deductible. Find My iPhone helps to locate lost/stolen phones, but does not guarantee you will get it back.