https://postcourier.com.pg/obama-putin-hold-private-meeting-at-g20/
https://www.cbsnews.com/news/obama-putin-have-private-chat-at-g-20-summit-turkey/
Arguably they did meet "in public." So we know they met, it was public knowledge. Yet we only have second-hand reports on what they talked about, no "transcript." No "translator notes."
We also know Trump had at least one meeting with Putin using a translator. Then asked for the notes. No transcript, just what Trump says the meeting was about. Apparently whatever was discussed Trump wanted to keep confidential...as did Obama at the time of his meeting. :shrug:
I believe Theodore Roosevelt was the first President to travel outside the USA, although there may have been foreign heads of state who visited the USA before that time. Are we aware of every conversation he may have had with foreign heads of state?
Woodrow Wilson met several foreign heads of state, do we have transcripts of every conversation/meeting?
https://history.state.gov/departmenthistory/travels/president/wilson-woodrow
Franklin Roosevelt met several foreign heads of state during WWII, are we certain that we aware of every conversation he had with Stalin, or Churchill? Any other head of state he ever met with? Or just the ones they had in group meetings?
It is entirely possible in all the above situations and in any follow-on Administration that a seated President had a private conversation with a foreign head of state for which we have no public (or private) record available.