You could be right...I’d have to dust off an old law book to see if a pocket veto requires Congress to not be in session. Since they never go out of session any more, there would never be a chance to have one occur. I don’t recall ever reading about a law coming into effect because the President didn’t sign it in time, but maybe that’s how it works. I would have known when I took con law, but that was a long time ago.
Forgive if this has already been answered; IF POTUS (or a governor in most states) does not wish to appear to endorse a law but does not wish to veto it, they can simply leave the legislation on their desk. I think it is 30 days and then the bill automatically becomes law.