It is an important verse to correctly interpret. As you say, Jim, there are some who Satan has told there is no hope because after they became a Christian, they went back into the world. Here is the way I understand this and it gives many hope when they had none.
Is it true that many have been buried alive? If so, why were they buried alive? What does it mean to be buried alive. From what I have seen in the last 30 years, the church remains in a Laodicean condition. I think you can see where I am going with this. So many have become discouraged, often because they could not do that which they knew they ought to be doing. After being in the world, Jesus was still calling them back. But, as you say, Satan is telling them there is no hope and this verse is one of his lies.
Look closely at the verse and then consider if they really had "tasted of the heavenly gift, and were made partakers of the Holy Ghost." Most were not truly converted, so does the verse apply? You want an example from Scripture. How about the thief on the cross? Was he an Israelite? If so, then did he not think he was entitled to heaven before he fell away? Did he fall away from his religion? Now, the question to ask if the first two are true, then was he saved? While he knew of Jesus, he had not given his heart to him and was led astray by his evil friends. He had not tasted of His great love, did not know Jesus had to die. He had been deceived as most were. He did indeed go back into the world. What changed his life? He had not known these things in the past.
Hope this helps, Jim. I am sure that many others will be blessed to have this sorted out. It begins by understanding what it means to be converted. The Laodicean does not understand, for he believes he is just fine (converted) when in fact he is miserable, poor, wretched, blind, and naked. If the Laodicean goes into the world, then the verse does not apply.