I have to disagree with that Tiger. It is possible to capture a ghost in a bottle. After all jinn were captured in bottles and lamps so it makes sense that a ghost could be trapped in a bottle as well with the right spells. It wouldn't take as powerful a spell as you would to trap a jinn.
Now Secret I'm guessing that you've seen or heard about places selling ghosts in a bottle. While a few may be genuine the vast majority are fakes.