I take full credit for this as I spent 10 minutes 8) finding these, and freaked when i found them.

i have decided to release my ways of doing the glitch. Have fun guys Thank and post if it worked!

Way one: Doesnt work most of the time, but its what made me want to find another way

Tut 1
Need:
2 people

Step1:Invite a friend
2: Start a private match lobby
3: Make gamemode whatever you want
4: Switch to combat training
It will disconnect you both and give an error saying the selected game session was full. Second player presses A and boom, S&D lobby, or w/e

Tut 2: Works 100% of the time, if done right.
Step1: Invite second person.
2:Switch it to private match.
3: Make the settings whatever game mode you want
4:Go to: Switch lobbies - Combat training, and hover there
5: Now when you press A, press B up A as fast as you can.
If done right, you will both be disconnected, and your friend will have a message saying something like the The party is no longer active. He will then be in a lobby by himself.

EDIT: If the non-host ends up in a player match, have the original host join back and have the non-host back out. That should fix it.

Credit again goes to me, and my patient friends. Message GT 'Deathsbugsy' for invite[b]