When using p4v to sync a project onto a 2nd machine I was surprised to see that files I had checked out on my primary machine were not included in the "Get Revision" (Get Latest Revision and Force options selected).
This seems like an elemental thing to get working but I can't find how to force this other than perhaps tagging the source tree and getting that, which I don't want to do if I don't have to. . .
This is an elemental thing. Syncing on one computer is in no way influenced by what you have open for edit on another. Syncing retrieves all those files regardless of who has them checked out, unless you have confused the server by messing with files outside the Perforce client. However, you said you used the -f option, which would solve that problem.
Are you sure you don't have those missing files open for add and not for edit?