I’m pretty sure that it eventually fixes itself if that account gets some activity.
Made the title clearer
[Moved to #academy:questions-answers as it’s not an in-game bug but a question about RealmEye graveyard]
No, you’re thinking of the No data available yet message.
The message Data for this account has not been migrated means that the player was inactive during the time that the game devs transferred all the player accounts onto the current database, and if the player missed that window, all their old deaths are forever lost, sad to say. There’s nothing that can be done by RealmEye because the data isn’t there any more on the game’s player database.