Zundrah,
This is a very good question, needing some background understanding.
The “keys of the kingdom” came from Christ, and according to Matthew 16:19 those keys were given to Peter. The verses there show that the keys conferred the power to “bind on earth” “whatsoever…shall be bound in heaven.”
The question is, what happened to those “keys” and could they be “lost” if they were not “used” properly?
What was Christ’s intent by giving the keys to Peter? When He commissioned the apostles to teach all nations, as related in Matthew 28, we read:
18 And Jesus came and spake unto them, saying, All power is given unto me in heaven and in earth.
19 Go ye therefore, and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Ghost:
20 Teaching them to observe all things whatsoever I have commanded you: and, lo, I am with you alway, even unto the end of the world.
The commission was clear: go, teach all nations, baptize in the prescribed way with the power and authority given by Christ, teach them to “observe all things whatsoever I have commanded you”.
It is clear from Acts 1:20-26 that Peter and the apostles understood that they had the authority to ordain another apostle to replace Judas, and did so by ordaining Matthias at that time. It is clear reading the New Testament that Paul was later ordained an apostle, though it is not clear who had died such that his ordination was required.
The epistles of Paul and of Peter show that these apostles had ongoing concerns about keeping the doctrines taught among the people and the ordinances practiced among them correct. This would be in keeping with the commission they had received from Christ.
Here on this website is a set of paragraphs discussing how the early church decided to begin using the name “catholic” and how some early leaders viewed their role, as well as noting the problem with “schisms”.
catholic.com/library/What_Catholic_Means.asp
May I suggest that by the time all the apostles except John had been killed and as the communication methods and travel methods did not facilitate keeping all of the doctrines and ordinances purely and consistently the same as those which had been taught by Christ, and as leaders thought best to begin using their personal judgment in questions of doctrine or ordinances rather than relying on revelation by the Holy Ghost as Christ and the apostles had taught, then inconsistencies and disputes arose within the different areas where the gospel was promulgated. Thereupon, the decisions made by the leaders to settle these disputes and inconsistencies using council meetings where votes were taken to settle upon doctrine, and using “tradition” as the ensuing doctrinal foundation, and where this doctrinal foundation of “tradition” rather than relying on revelation and direct guidance from the Holy Ghost as had been taught by Paul and Peter, resulted in the church being led by the “wisdom of men” rather than by the “wisdom of God”.
The commission received by the apostles thus was no longer being carried out after their deaths because the “wisdom of men” was the basis of doctrinal and ordinance settling of questions. The authority and power conferred by the keys was thus lost gradually, over a period of years, until no one had the real keys although they still taught many of the correct doctrines (but some were not correctly taught or practiced).