There are folks who are saved but aren't converted. Remember what the Lord told Peter.
Luke 22:31, 32 - KJV
And the Lord said, Simon, Simon, behold, Satan hath desired to have you, that he may sift you as wheat: But I have prayed for thee, that thy faith fail not: and when thou art converted, strengthen thy brethren.
And we know that Peter was converted - so much so that our Lord trusted him to write epistles that are now in the Holy Bible. Peter didn't write those epistles UNTIL HE WAS CONVERTED.
And then - CONVERTED Peter had this to say, among other things:
The Acts 3:19 - KJV
Repent ye therefore, and be CONVERTED, that your sins may be blotted out, when the times of refreshing shall come from the presence of the Lord; (For emphasis, I capitalized CONVERTED here.)
Peter wasn't just writing the truth - he personally KNEW that truth because he had PERSONALLY lived it - and thereby became spiritually qualified to express it.
Church building attendance does not guarantee salvation. There are some holy folks who don't go to church buildings but shall surely enter heaven. And some holy folks who do attend church buildings shall surely enter heaven. Assembling with other believers doesn't necessarily need to be in church buildings. Jesus ministered to people in boats/ships, on mountains, in the garden, and out and about elsewhere. In the book of Acts, they assembled in houses. The focus is not where but who - GOD is the most High WHO we are commanded to worship. Steadfastly obeying Him and His Holy Bible content assures entrance into heaven.
Be not deceived, some church building attendees are not saved. Some of them shall get saved and enter heaven and some of them shall not be saved and won't enter heaven - that's Holy Bible truth.
Note: People who are newly saved and those who haven't yet reached levels of spiritual maturity may be led by GOD to attend church buildings to gain a solid foundation about GOD and His ways. It's vital, though, to seek the Lord for guidance as to where to attend. Also, it's vital to spend quality personal time, one on one, with GOD in prayer and meditating in Holy Bible content - day and night as instructed in Joshua 1:8. There is no substitute for knowing GOD for ourselves. Spending quality personal time with Him seven days a week is vital.
* Beware of Bible translations. The NIV Bible removed Acts 8:37 and Matthew 18:11. Those scriptures are NOT in there. For more about Bible translations, here's a link http://www.newbreedwarriors.blogspot.com/p/bible-version-information.html
2 Timothy 2:19 - KJV
Nevertheless the foundation of God standeth sure, having this seal, The Lord knoweth them that are his. And, Let every one that nameth the name of Christ depart from iniquity.
James 1:27 - KJV
Pure religion and undefiled before God and the Father is this, To visit the fatherless and widows in their affliction, and to keep himself unspotted from the world.