Recovery during prayer has two different cases:
• A person who was praying sitting with actual Ruku and Sujud, then becomes able to stand, stands and continues the same prayer.
• A person who had reached the stage of praying by head gestures and then regains the ability to perform actual Ruku and Sujud cannot simply build on the gesture-prayer; the prayer must be restarted.
The difference is important because actual bowing/prostration and symbolic gestures are not the same level of performance.