Yep, it's a possibility not, but I'm not sure that it was ever covered where they were. Like I said, I just assumed they were always on Alderaan. Could be wrong.
Even though the film doesn't spell it out explicitly that Bail and Breha Organa are on Alderaan the precise moment it is destroyed, I'd say it is pretty clear they are.
"... I have placed information vital to the survival of the Rebellion into the memory systems of this R2 unit. My father will know how to retrieve it. You must see this droid safely delivered to him on Alderaan..."
"... When we heard about Alderaan, we feared the worst.
In fact, in the published version of the shooting script, Willard's line actually read: "When we heard about Alderaan, we were afraid that you were... lost along with your father."
I mean, it's part of Leia's entire motivation, just like Luke losing his foster parents and declaring "there's nothing for me here now".
Leia's original mission was to see the plans delivered to her father - I'd say that is a huge part of the plot, that everything now falls into the younger generation's hands, their guardians no longer around to help them (or hold them back).
Leia's got to do this thing herself now, her adopted parents are dead.
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