Why on Earth is there a timer for retrieving items after being demolished?

[Vidu]

My understanding is also that the item storage from the NPC in question is bound to the plot of land, not the person (otherwise it would get complicated for FCs, I reckon). Since its possible that your house gets demolished, someone else buys it, but doesnt take care of it straight away, so the house gets demolished again you could probably run into problems with the reclamation of housing items if the previous owner didnt clear out the storage before... so... they put a timer on that.

While this might not help you in your current situation, this is really a good place to remind people of apartments again: They wont go away, they're here to stay. If you're worried about event items being lost: Buy an apartment and store them there! (Or, if you want to actually use them in your house, store some duplicates - my apartment is filled with nothing but event items)
Since all seasonal events only require a level 15 character whos completed the mainquest far enough to travel to the three initial citystates, it might be an idea to create an alt solely for the purpose of holding onto seasonal event items - might not be possible, depending on your sub and/or your server and/or your alt-addicition, but its an option aswell.