Random thought that might not make any sense (pardon any wrong things here):
You know how Matt was rescued by a rebel group? What if he was also trained to fight to the point where he could fight as well as the people from the Blade of Marmora? Imagine when Pidge ‘rescues’ him (or at least if Voltron forms an alliance with their group) all the sparring sessions - he’d be able to beat Keith, who’s basically the team’s best swordsman. (Pidge and Shiro’s mind would be totally blown because this is not who they knew, yet it’s still Matt.)
Or it could be that the rebel group forms an alliance with Voltron before Pidge or Shiro knew that Matt was in there. And since Matt is probably really smart (as smart or more so than Pidge probably) he’d probably get a high position in the group, like a tactician or one of the commanders. And then, what if the mission both groups are carrying out goes south. What if just then Matt from the command center realizes something wrong after staying quiet and just yells, “Something is wrong, you need to get out of there immediately!” And Pidge is taken by surprise and manages to gasp out “Matt?”
“Katie? What are you–”
“Matt, this is where you’ve been all this time–”
A voice full of awe. “Katie. You’re a paladin of Voltron. You’re… you’re crossing galaxies beyond what Earth would have even imagined, and you’re… you’re… actually making change.”
“Matt, please tell me where you are right now–”
An explosion. “Katie– Team Voltron, you need to get out immediately–”
“Matt, Matt, please–”
“Find Dad, Katie. For both of us.” A soft smile. “Tell Mom I love her.”
A whisper. “I love you.”
They don’t even get to meet because they’ve been communicating through an intercom. The signal goes flat.
Pidge stays silent for the rest of the mission. She doesn’t hear from Matt again.