ottomatic said:
I don't believe that this dream scenario ever happened to you; and your name even implies you're a diaper-lover. People who wet the bed so in their sleep because they don't wake up.
I'll skip over why someone might register for a site just to accuse a not-new member of lying, other than to say sometimes things you think are unlikely do happen to someone, and attacking someone directly isn't a good way to make friends. The best option is to ignore them or only report it if they are consistently posting dubious things, something this member certainly isn't.
That aside, your assertion that this never happens is false. I would be willing to bet you have experienced almost the exact phenomenon described in a different way. Have you ever heard someone calling you in a dream, only to wake up soon afterwards and realise they were actually calling you irl - or heard an alarm in a dream only to wake to find someone's car alarm is going off down the street?
The point is that your brain doesn't stop processing auditory information and other inputs just beacuse you are not conciously aware of it, i.e. asleep. It's actually pretty smart about it too: studies have shown that a child can be woken by their mother's voice when in a sleep deep enough to otherwise be oblivious to a loud alarm. Your subconcious, however, can still become aware of certain information and that's how it enters your dream without you realising it's real.
Consider that the bladder needing to empty is just another signal, one that should wake you up. Particulary in young children, the most common cause of bedwetting is that this trigger doesn't wake them up when it should - more commonly with deep sleepers.
It would be strange to think of this as a binary process where it works or doesn't - the biological world is often pretty grey with things working some of the time and not others. This signal can also not be enough to wake you directly but end up in your subconcious and you start dreaming of running water or other similar themes. Even aduts who don't wet the bed can get warnings like this and wake up from it eventually - I have. It's very believeable that someone, even an adult, could wake up just a bit too late from it. There are many tales of heavy drinkers wetting the bed because they needed to go a lot more urgently than they are used to.