Must be my imagination is an article in Resident Evil Recollections. It was uploaded on 29 August 2016.
Leon is accompanied by a couple of cops at the start of Resident Evil 4, who seem to think they got the "short end of the stick" by being assigned this task.
When one of them stops to take a leak, he seems to feel something but brushes it off as "just his imagination". He probably should have paid more attention, there's something out there...
Such a shame, I really wanted to see more of these three bantering togther.