1) Sure you got the right valve, not the winterize pump valve? If you put water in the top and it runs right out the bottom, then that's a pretty good sign the drain is still open.
2) Did you fill it long enough that it may have just overflowed out the overflow line? This would be a very delayed running out after filling for a while.
3) Conversely, gauge will still show empty if you are below 1/3 (if 1/3 if your first light). (Or the gauge could be broken or a loose wire etc.)
2016 Forester 2401R