The stored contents are only deleted if they are of the same refined metal as the storage tile (e.g. copper stored inside of a copper storage tile, but not glass).
Consider the following example.
- start with a copper storage tile and 200 kg copper in the stored contents;
- order replacement of the storage tile with a sandstone tile;
After the storage tile is re placed, observe that
- the building materials of 100 kg copper + 100 kg glass are dropped as debris;
- the stored contents of 200 kg copper is missing;
- deconstructing the sandstone tile does not reveal any hidden/buried copper;
The attached save file should reproduce the scenario the example described with a replacement order queued. Once the game is unpaused, the dupe will start replacing the storage tile with a sandstone tile.