Continuity mistake: When Hank takes Connie to the doctors, he is in the waiting room. After Connie and the doctor come out they open the two doors and stand in front of the doors. Towards the end of the scene as the doctor is about to leave them, they have all moved far a short distance from the left of the doors.
Continuity mistake: After Connie tells Hank she is experiencing her first period, Hank consults the book that Connie's parents left for Hank. There is a close up of the folder from Hank's point of view and you see there are not many pages on each side. You can tell this as you can see the binder's covers below the papers on each side and there is not much material on either side. The next shot that shows Hank skimming through the papers each side of the folder has a lot more papers on each side than the previous shot.
Answer: Couple things, first only Peggy knew the truth about Hoyt (Luanne's father) being in prison and Peggy is the one who said he's on an oil rig. But, Hoyt is Peggy's brother, so she could have been trying to hide the fact her brother is in jail. Lucky (Luanne's husband) deduced Hoyt had been in prison, but seems to be the only other person to know the truth, so when Hoyt went back to prison, he kept Peggy's lie up to spare Luanne. Additionally, Luanne was there when her mother stabbed Hoyt and was arrested, so it's not like someone had to break the news to her and they couldn't hide the fact. With Hoyt, even if Peggy wasn't trying to protect her brother's reputation, she didn't want Luanne, who is a sensitive and emotional young woman, to have to deal with knowing both parents are in jail.
Bishop73