The Rust update made some changes in the terrain that made the caves change in size, So if you built in a mountain opening or cave You might find that they may have overlapped your Furnace or doorways, Boxes. If that has happened to you let me know and I can retrieve your items for you.
Mine was not too bad. Picks below. But I had to help a player get stuff from his Furnaces because the rocks covered them up completely.