ownCloud doesn’t support Google Drive’s versioning.
The problem with Google Drive’s versioning is that it creates several files with the exact same file name. ownCloud cannot work with a remote folder containing several files with the exact same names, so the GDrive external storage module will ignore such files. This is why you see them disappear.
Now in the case of versioning, one could say that maybe ownCloud should only access the latest version of a file. Maybe. But it’s not that easy: it seems that GDrive also allows you to simply upload several files with the same name even if they aren’t really related or versions of each others. In this case, how to decide which file to use ?