The cygnets were found alone in the abandoned factory and perhaps they were lost themselves and their family didn't wait for them, it also happens. At least I often saw some ducklings swimming away from their mom and siblings rather far while their family is sleeping on the bank, cygnets may easily "go to travel". Anyway, the result is the same.
She came home around midnight and was a little crazy, jumped around, moved hay. In the dark, I wasn't sure it's the storklet.
It wasn't, 'cause it had no ring and its legs were more red. It was an adult one. Usually one of the parents visits the nest to prepare it for the next season, but somehow KarlII in Karula didn't do that.
Today Drobek may have a rest before starting migration.