I'm having trouble finding it but there is a labeled floorplan out there somewhere that shows it. Essentially it was just outside the WC in that hallway near the boiler room. Hard to say why French may not have seen it, but I suspect that he was called to the scene something like 6/7 hours after her death, so it may not have been very wet. There was carpet it could have seeped into and just looked like a normal dirty basement carpet.
View attachment 103444 This picture was taken before her body was discovered, so likely not long after the cops got there. The carpet appears to be gray. Also, this is not a large amount of urine. Its suggested that she must have recently voided her bladder (ante-mortem) because there was so little urine.
I noticed in the lifetime movie teaser they make the urine in her bed very obvious...
I know that some investigators have said her sheets "reeked of urine" but I don't know if there were tests done or anything. As poor a housekeeper as PR was I don't think she would leave wet sheets on the bed...LHP said that was the only housework she did, cleaning JB's sheets.