It is valuable to remember that there are many instances of emergencies, deaths, and various 'intense' events that happen to friends & loved ones that we do NOT have any inkling of until informed later. It seems that the 'knowing', if it actually does happen, is not automatic or predictable.
   If it happened regularly or someone could reliably demonstrate it under controlled conditions, I submit that it very well might be tested and/or measured experimentally. If one brain/mind can 'send' a.... whatever... to another, that 'whatever' ought to be detectable. We DO detect brain waves and measure electrical activity, and progress is being made for quadriplegics to do things like operate computers by 'mind power'. Who knows what will come next?