Virtual copies don't get saved to the metadata, like plenty of other work, so that explains what's happening. If you want VCs in another catalogue, use File > Export as Catalog which exports all your work. You can then open that catalogue itself, or bring it into another catalogue using File > Import from Another Catalog. Of course, having the same image catalogued in more than one place can become confusing, and it's usually better not to have multiple catalogues if you really don't need them.
