Nick attempts to call Daisy shortly after he has discovered Gatsby's body floating on the air mattress in his pool. Nick's call is based on his reflexive assumption that Daisy would want to know what had happened.
However, Nick is informed that Daisy and Tom were not at home. In fact, they had packed their bags and left earlier that day without leaving any information about where they were going, when or if they would be back, or how one could get in contact with them. All Nick can do is leave a message asking Daisy to get in contact with the person who answers the phone. He waits and hopes for a long distance phone call or a telegram, but neither ever arrives.
Months later, Nick has one final encounter with Tom Buchanan. Tom never learns who was the driver of the car that killed Myrtle, so feels he was justified in telling Mr. Wilson that Gatsby was the driver. Nick concludes that Tom and Daisy
were careless people... they smashed up things and creatures and then retreated back into their money or their vast carelessness, or whatever it was that kept them together, and let other people clean up the mess they had made.