The ability to retain the information might be a technical limitation with how they've designed housing since it's instanced and stored separately from character data. I doubt they can just take the items out of storage and move them to your character/retainer inventory (you may not even have room there).
Is it something that could be changed? I have no idea. I don't know how everything works on their end.
At least most of what you lost can be acquired again. I don't know what to suggest about the seasonal items since the Calamity Salvager seems to be limited to items that can be equipped. Sometimes things we've earned in a game are taken away and there's no much we can do about since in the long run, we don't own anything in the game. We're only "renting" use of it.
While in game:
System->Support Desk -> Contact Us -> Leave a Suggestion.
