DataBuffer getOldBuffer(DataBuffer buf, int index) throws IOException {
		try {
			int vfIndex = bufferMap.get(index);
			return getVersionFile(vfIndex).getOldBuffer(buf, index);
		} catch (NoValueException e) {
		}
		if (Arrays.binarySearch(freeIndexes, index) >= 0) {
			buf.setId(-1);
			buf.setEmpty(true);	
			buf.setDirty(false);
			return buf;
		}
		return null;
	}
Get original buffer associated with the specified storage index in the 
original file.
@param buf data buffer
@param index storage index
@return data buffer or null if buffer is not empty and has not been modified
@throws IOException if an IO error occurs
Ghidra/Framework/DB/src/main/java/db/buffers/VersionFileHandler.java