hello? this experience is a trick by your brain to keep you sleeping! believe me. i have experience with this.
once my mum send me an SMS (she was on vacation) in mid night and it got integrated into my dream, so i dont wake (i got an SMS in my dream ), then i realized that this is impossilbe, cause my handy is almost always off (especially when beeing at school) and when the the "SMS-sound" occured for the second time i waked up.