Have you ever known anyone who committed suicide and the reason was never discovered, as in no note was left behind, etc? ~

Unfortunately yes.
Sad.

Yes, she was in psychological pain.  She did off herself on one of her depression jags and gin binges.  No note, etc though we all expected it sooner or later

Yes and No.  It is still a mystery as to whether it was sucicide or murder.

No one I know has ever committee suicide with or without a note.

My half-brother's son was found hanging by the neck.  There was no note and some thought it was suicide.  Other's thought it was an accident that happened during some kind of erotic session.  I'd never heard of that and have not bothered to look it up.