I don't think this could be a good reason because your BP is scanned every 100m at CDG, so there is no way you can go wrongly to a "wrong" terminal. But, yes, there is always a way to exit. It happened to me twice, waiting in one of the lounges in 2E and then learning that your flight is cancelled or so delayed that you decide to cancel pour trip. But then you have a good reason. In the OP's case, there is no good reason outside of "inventing a nice story". And, when you return, when your BP is scanned at security, you can be "flagged" as already passed through (although I'm not sure about this one-no personal experience).