So bad.... do you think they would have found their way to GARF?
Probably -- a number of the other girls' diaries did.
What we don't know is HOW MANY diaries Maria and Anastasia burned. Three of Maria's diaries are held at GARF, so obviously she didn't burn all of hers. So far, none of Anastasia's diaries have been located. Maybe she burned them all, but maybe they were lost, or maybe they're still lurking somewhere....
Incidentally, three of Aleksei's diaries are known to have survived the revolution: 1916, 1917, 1918. GARF has the 1916 volume, but the current location of the last two are unknown. Luckily, excerpts from his 1917 and 1918 diaries have been printed in
Le Tsarevitch.