Help with missing discus?

Unfortunately, I do believe your other fish have eaten your discus. If you leave your fish alone for 5 days, they will become hungry and start picking on their tank mates. If the discus was smaller than the other fis, or weaker, then it is most probable that they ate him. I am sorry to tell you that. And trust me, 5 days is enough time for the fish you have to completely consume a discus. Sorry.