Yeah, phrases must be heard in-game or they don't appear when you get to the painting. In games where the party went in through the back door and killed Sherincal later, we didn't get the "From the Sea of Moving Ice".
So if he killed Oria really fast and she didn't have the chance to say the magic words, there's no way for him to get them now, except by restoring and killing her again, a bit more slowly
Nightowl2