Can't imagine waiting 24 hours..I would be super anxious. Call them back and ask them straight up what the issue is. talk to your ob or whoever is oncall. You have a right to know. Good luck.
There may have been something off in your quad which checks for syndromes. There are allot off false positive though so they usually do other tests. Hope everything goes well. Try to breath until you get there.
Unless they did an ultrasound I dont think they can see if your baby is dead so try not to stress too much!! :) I hope for the best!
Are you going to see them today? Usually if theres something theyll call you or mail you a letter but they never asked me to go in so I would say go see them ASAP I hope you amd your baby are okay!