Well, "The R's" didn't call, Patsy called. Of course they can't both call but if PR wrote the note then she'd be very aware of the warnings she herself had written. It doesn't seem convincing, to me, that PR wrote all those warnings borrowed from movies, then ignored them altogether. So, at least one possible answer to your question is that PR didn't read the warnings (she claimed to have only read far enough to realize JBR was kidnapped) IOWs PR may not be the author of the RN, and that would explain ignoring the warnings. If she had written the RN wouldn't she at least have mentioned the need for unmarked cars and doing everything on the QT? Even if JR had written the RN and PR was in on the cover-up she'd at least have tried to make it look like they took the RN seriously.
IMO the body wasn't to be found in the house at all. It simply makes no sense to let the police see a fishy RN then a dead body. Fishy RN + dead body = Family member killed her. Why would either or both R's present such a scenario to police? Why both JR and PR were not immediately arrested is hard to understand.
The death of JBR could not be attributed to LE presence after the body is discovered on the premises. At autopsy a reasonable estimate of TOD would be made and the police would know she died hours before they were called. Thus, she cannot have been killed because the instructions were not followed. She was already dead before the 911 call.
If the body were found outside the home -whether hours, days, or weeks later, it would look as if the "kidnappers" had killed her to prevent her from identifying them.