It is quite true, unless there is available open honey or nectar, or attendant worker bees to feed them they won't last very long. Queens can eat honey/nectar from honeycomb cells, and they'll sometimes try to eat from queen cage candy (perhaps with some success), but even under the best alternate situation, they need attendants to properly care for them. Even with available feed (queen cage candy), I wouldn't expect a queen to survive for more than a few hours, unless she had several attendants and candy to feed those attendants.