John 14:26 But the Advocate, the Holy Spirit, whom the Father will send in my name, will teach you all things and will remind you of everything I have said to you.
Is there anyone else but those apostles that could "remember" what Christ said to them?
>>The source has been lost to history.<<
No it hasn't. Even if you disregard those books not self identified as to who wrote them we still have all we need.
Your response doesn’t answer all of the questions.
How do you know they’re from the apostles?
How do you know they’ve been written into the Gospels faithfully?
What is the source for verifying all of the above?
Can you provide authentic, reliable, information documenting who wrote the gospels, when they were written, and where they were written.