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You can get your wizard underground and then you should be able to click on the item and pick it up without needing an attic interface. There are 2 ways I've used to get under the guild island.

You can get on a carpet and move it up over the invisible wall on the edge of the island (it isn't very high, thanks KI!) then down a ways, make sure you are low enough that you aren't going to pop up to the land surface) and then through the visual wall of the island and then you should be able to see your lost item. The island is pretty big so do this near where your item is, and also avoid the areas near the crafters and the gates, there are some additional walls.

The second way is to use a jump or text detector, set it to port player to your carpet, then use advance move to sink the carpet underground and port yourself to it. That's faster and easier for me but you need to use castle magic and also sometimes targeting is lost if you move the carpet too much so it may be better to use the first way if you aren't comfortable with castle magic and its quirks.

All that said, an attic would be really nice to have and also considering how little storage there is for guild items, it would really help if guilds want to set up holiday displays or something and not have to keep trashing stuff.