If there in the future will be technology able to work outside the box of linear time the future might alredy be affecting our past through humanitys subconcious (which also exists outside linear time) and something like a quantum-AI or people from the future could be what people in our history saw as gods and dont even notice(well some think their talking about aliens) because we are so used to technology being all around us and are to busy to look at the bigger picture.
Also: if something that advanced wouldnt want to get noticed it wouldnt get noticed even if it was currently affecting every living thing at the same time