One of the quick yes/no questions (tried googling and Merlin(g))…
It seems, that when I reload a saved project where one or more of the recorder buffers held a recording which was not saved, this recording is brought back?
Can that be the case? If yes, where did it store that file?
nah man recorder buffers are stored in the ram and never anywhere else unless you intentionally save them unfortunately. save your parts, save your buffers, save your project
But, what if I save a project with something in recorder buffer 1.
Then clear the track
Reload the project
Then I find the same recording inside recorder buffer one.
This doesn’t happen to you?
nope, wipes out even without a full restart
Haha, I can’t seem to replicate this either now.
Some mess about my understanding of parts I guess.
Clearing the slot on one part, doesn’t clear it in the other parts.
Your recording has been probably saved and assigned to self > loaded in the recording buffer everytime you reload / restart.
I read that as restart. 
Checking…
I had a doubt but yes with power cycle / reload / project change / file manager / memory config change…
you loose buffers.
Thx @sezare56 … But clearing a record buffer in one part - also clears it in other parts?
Yep. Cleared everywhere in the project.
Recording buffers are in Flex slots, common to the whole project (Static slots are common too).