A few questions may help:
How long have you had it?
What kind of soil is it in?
Where do you live?
Can you post a pic?

Generally, fukien tea trees pitch a fit every time they are moved around. I would say make sure you have it in fast draining soil, get it in a warm, well lit spot and stop messing with it. Scratch the surface of the trunk and see if there is any green under there. If so, you are probably ok as long as you get it back on track.

I am a total newbie at Bonsai but I think any plant that has gone thru what this one has will be a tad stressed. Poor thing is wondering WHAT NEXT? LOL I have a Fukian tree and it seems to be OK after 2 years of living with me. Good luck with yours.

Lots of plants throw a fit when moved around and fukien tea is well known for it. Light and temperature change can cause them to lose their leaves. The plant is still probably alive. I would stop watering it. Instead put it in a lighted cooler area and cover it loosely with a transparent plastic. I usually use clear grocer bags and clean it with a diluted bleach. Then wash it with plain water, shake off the excess water and cover the plant. You may need a stick to prop up the plastic since you do not want it touching the plant. Every few days check to see there is any mold. If there is give the plant a rinse without wetting the soil and start with a new bag. Usually, finicky plants start growing new leaves in a couple of weeks. Once that happens, take the plastic off and mist it lightly for next few weeks and it will adjust its new location.

I have revived many plants using this method and also a lost a few. To me the #1 plant killer is over-watering.

A run of bad luck I guess and too much cold. I grow a few larger ones here and go thru this every monsoon season. A 15 or 20 degree drop in temp for a few weeks and they, plus a few others, go through a period of leaf drop. They're in pots which drain well so over-watering isn't a problem.

Easiest was to dry out the soil -now - is to take something the size of a pencil and make a number of holes down to the bottom of the pot. Move it in a sloping circular motion so it's pretty big at the top. Air flowing over these will cause evaporation and you will get a little more air to the roots.
Or, just take something, chopstick, spoon, whatever and simply stir the soil top to bottom. Put the roots back under when your finished. This will also give you a good idea of just how wet the soil is.

What would have probably saved the tree, in the beginning, would have been to construct the tent the other person suggested. You could have put a 60 or 100 watt light in there, under the pot/tree, and probably really helped save it right off the bat.

I would suggest staying away from cleaning the tent/bag with bleach. Most cheap plastic will absorb some of it, the last thing you want is a chemical that toxic in an enclosed space with the plant.

At this point changing pots or re-potting would only be an excercise. See what happens in the future.
Good luck...Bob

I would suggest staying away from cleaning the tent/bag with bleach. Most cheap plastic will absorb some of it, the last thing you want is a chemical that toxic in an enclosed space with the plant.

I agree that cheap plastic will absorb some of bleach and other chemicals. But when diluted for household cleaning it is not that toxic and it will break down pretty quick. Regular bleach is toxic when it reacts with other household cleaners like ammonia. Anyhow, probably it is safer to avoid it anyway. Alternative is hydrogen peroxide.

For small plants I use an empty two liter coke bottle with the bottom cut off and the cap removed as a humidity tent.

Hang in there it will come back.