At the end of the episode it is revealed that Kendall thought he and Jo were together so he thought he didnt have to ask and they are then confirmed as a couple.

Why did Kendall pick up over Lucy?

Kendall must choose between Jo and Lucy while Carlos and James friendship is tested. With Jo returning to the Palm Woods because of her movies production being canceled from the set burning down Kendall has to choose between Jo and Lucy.

Does Jo come back on BTR?

She makes her return in Big Time Surprise at the very end of the episode seeing Kendall and Lucy kiss.

Did Camille leave Big Time Rush?

At the end they all made peace but Logan thought this was the right time to break up. As of the episode Big Time Returns Logan and Camille are officially a couple once again but according to Camille this time itll be different. In Big Time Dreams Logan and Camille end up together at the end of the series.