I recently bought a template/theme from virtual planet for my store. It wasnt working so I contacted them. I gave them permission into FTP and he informed me I have some Core VM files missing. I am using the latest 2.0.20b. Is there a way I can "reinstall" core files without losing data (products/users etc) ?
Install the main VM and the aio component again using Joomla's extension manager. You will not lose any data.
If that is the VP Promart template I see it was released in September 2012 - so I'd check with them that their overrides will work with the current VM versions - the one in use back in September was 2.0.10