Matthew 27:62-66 Now the next day, that followed the day of the preparation, the chief priests and Pharisees came together unto Pilate, Saying, Sir, we remember that that deceiver said, while he was yet alive, After three days I will rise again. Command therefore that the sepulchre be made sure until the third day, lest his disciples come by night, and steal him away, and say unto the people, He is risen from the dead: so the last error shall be worse than the first. Pilate said unto them, Ye have a watch: go your way, make it as sure as ye can. So they went, and made the sepulchre sure, sealing the stone, and setting a watch.
There is no record here for the activities, thoughts or expressions of Christ’s followers. This first dark day is full of activity for the enemies of the Cross. They will enlist the help of their sworn enemies if need be to see that Christ is denied.
If anything can be said of the apostles, at least those that were Jewish, is that they went back to observing the Sabbath and did nothing. Christ was gone, they had no leadership, no direction, instruction, and nothing to do. They ignored everything Jesus had taught them and fell back into old behaviors.
One could also say they were patiently waiting on the Lord but in order to support that thought, we would have to see their reactions on the second day.
If there are any lessons here for us to see during dark days would be personal. What do you lean upon without Christ? I cannot answer that for you.