What happens to the XP points of the second player in dual screen?

When you play on dual screen, the second player gets some XP points depending on his performance during the match.

I think that the main player, the one who owns the account, gets those points to earn levels.
But what happens with the XP earned by the second player?

Are his points lost when the main player plays alone (one screen) in online mode?

Solution 1:

If the second player is logged in with a regular account, their stats will be saved. If they are simply using a guest account, the XP will be lost.

However when you log in as a guest at a later date, you will be at the same level as the main player and have all of their classes.