I've never been in ATTI mode, but have an idea:
If you have sight of the drone, put it into an easy circle: Right stick forward, left stick to the left. This should produce a skidding counterclockwise circle as the drone drives forward while yawing left. From your perspective, the circle will be nearly edge-on, and the craft will appear to move left, stop, move right, stop, move left, etc.
When the line of sight to the drone appears to stop drifting to your left, neutralize the left stick just before it starts drifting to your right. At this instant, the drone course will be pretty much toward you, but the drone heading will actually be pointing to its left of the homeward heading, because of the skidding nature of its turns. So, you'll probably find it necessary to give it a bit of right yaw (the left stick move right) until your visual bearing to the drone remains constant. Neutralize left stick and continue holding right stick forward. Confirm the distance is closing:
As the distance closes, the elevation of your line of sight should begin to increase, and the RC display should confirm the distance is closing. Soon it should be close enough that you can fly normally.
I've never been in ATTI mode, but this procedure worked well for me when the DJI app disconnected from the remote. Seems that it might work with luck even if you have lost sight of the drone, if you monitor the distance readout.
Be careful you don't inadvertently mix in some "down" command with the left stick. Keep the movement strictly in the 9 o clock or 3 o clock direction and check altitude indication.
Try this a bit in a safe area and controlled situation for practice.
Regarding altitude: best to climb if you are sure you won't climb into an obstruction. Also, you may regain sight of the craft, since it will more likely be silhouetted against the sky, rather than trees or clutter.