It’s a bit of an odd question.
Let me clarify the systems here: the vfs is used to define the filesystem. By mounting and/or unmounting things on the vfs, you can make files appear wherever you want in the filesystem tree, regardless of what files may or may not exist on your hard disk. The initial, default vfs mount exactly mirrors the filesystem provided by the OS, of course, but you can change that however you like.
This has nothing directly to do with the loader, or the model-path, except that the loader uses the filesystem as defined by the vfs.
So mounting a new volume into your vfs doesn’t change the model-path, and the directory you’ve just mounted is not automatically searched by the loader. However, you can load a file from any mounted directory by specifying its full path (which starts with a leading slash), or by putting the appropriate path on your model-path.
Try not to think about the vfs as something magical. The vfs doesn’t interact with any other systems in Panda. Think of mounting a multifile as being the equivalent to simply unpacking the contents of your multifile onto your hard disk in the specified directory. That would have exactly the same effect in Panda as mounting it.
The model-path is primarily defined by the model-path Config.prc variable. It doesn’t have any default value other than what is defined by the Config.prc file(s) that have been loaded. You must have set it at least partly, since it has ./Assets/particles on it, which is presumably one of your own project’s directories, right?
David