Not everyone who hears the Word of God produces/is saved.
MATTHEW 13:18-23 18Listen then to what the parable of the sower means: 19When anyone hears the message about the kingdom and does not understand it, the evil one comes and snatches away what was sown in his heart. This is the seed sown along the path. 20The one who received the seed that fell on rocky places is the man who hears the word and at once receives it with joy. 21But since he has no root, he lasts only a short time. When trouble or persecution comes because of the word, he quickly falls away. 22The one who received the seed that fell among the thorns is the man who hears the word, but the worries of this life and the deceitfulness of wealth choke it, making it unfruitful. 23But the one who received the seed that fell on good soil is the man who hears the word and understands it. He produces a crop, yielding a hundred, sixty or thirty times what was sown.
That passage, if you look at the context, is not talking about believers. Believers cannot lose their salvation (wouldn’t be worth much if you could earn or lose it, would it?) It’s by grace we are saved. Period. Yes, there are people who hear and know, but reject the Gospel. They were never “believers.”