Quick Answer
Return to the common room, enter the lift together, and step out on the second floor. In We Were Here Tomorrow, What Just Happened? begins with both players waking up again; the common room’s lift is now open and only moves with both of you inside.
How Do You Get Through What Just Happened?
Return to the common room with your partner, take the open lift together, and walk out on the second floor to finish the checkpoint. What Just Happened? is the first checkpoint in Chapter 4: The R&D Headquarters.
Return to the common room
Both of you wake up in the waking room again. From there, head back to the common room together. Your destination is the lift in that room.
After the facility restart, the return to familiar surroundings prompts the reaction, "Well, we're back to the start, but she's not here." Keep going toward the common room: the lift is open this time.
Get both players inside the lift
Enter the open lift with your partner. It only moves when both players are inside, so make sure neither of you is still outside before expecting it to leave.
If you are waiting inside a stationary lift, have your partner join you. Both players must be inside for it to move.
Once you are both aboard, the lift takes you to the second floor of the R&D Headquarters.
Your partner steps out of the lift on the second floor.
Shown at 166:37 in Aravien_’s video.Step out on the second floor
Leave the lift when you reach the second floor. Stepping out completes What Just Happened? and unlocks Recon & Disclose, listed on the achievements page.
The destination is summed up by the line, "Well, we're on the second floor of R&D headquarters, apparently." Reaching that floor and exiting the lift is the end of this checkpoint.
Continue with Crew Quarters for the next part of the walkthrough.
FAQ
Go back to the common room, board the open lift with your partner, and leave it on the second floor. Exiting there completes the checkpoint.
The lift requires both players inside before it moves. If one of you is still outside, have them enter.
Continue to Crew Quarters after stepping out of the lift on the second floor.