Q.Lemon tree
Can leaves grow back on stems even if there is none?

Certified GKH Gardening Expert
Yes, but you will need to get more light, such as a 100 watt panel or better. It will also need to dry out more between waterings. At least 2 or 3 inches down should be COMPLETELY DRY before watering again.
Correct these two things, and you will see a very fast recovery. Aside from that, correct fertilization will be another key factor. This article will give you more information on their care: https://www.gardeningknowhow.com/edible/fruits/citrus/growing-citrus-trees-indoors.htm