I think seperation after one day is a little bit harsh. There are many other circumstances that you are not aware of. The person could have been in an accident, could have an illness that requires them to be in the hospital and unable to call. etc. I know most will say, then the family should call, but if you are dealing with an emergency situation, the last thing you are thinking about is calling the employer of the person. It is possible that the reason will require you to give out FMLA paperwork because it could be an FMLA applicable absence.
In the past I have used the 3 day, no call, no show rule. We did still try to contact the person to make sure that there was nothing wrong.