The youngest daughter's boyfriend and father played a key early role here. The son cast doubt on the bike ride, based on the location where the bike was found (steep climb, and having to push your bike up the hill). He said it would be out of character for her to ride there, and indicated that she hadn't gone riding there before.
He also explained there were marital issues, and they had talked about separating according to the youngest daughter.
This would have obviously been key in catching Barry in those early repeated lies about the state of their marriage.
The boyfriend's father seems like a great guy, and prodded his son to be completely open and honest, despite being put in a bit of a difficult situation.