Hi Van
A hint to help find your queen. we use 8 frame boxes, also single brood box with Qx, so I sort of know where the Q should be, if for the sake of description, frame 1 is closest to you.
Take out frame 2, inspect, take out frame 3 but as you do look at the face of frame 4 as some times the Q is heading down the frame to avoid the light, inspect frame 3. Then take out frame 7 and inspect, this put a shaft of light into the hive. Hopefully now you have your Q trapped on frames 4,5,and 6.
If still no success inspect the back of 1 and 8. Next check she is not running around the bottom of the hive. A friend who is 3rd generation BK says often if you are looking for a poor Q then you will find her in the bottom of the hive.
Still no Q, inspect all frames as you put them back.