Perhaps this sounds confusing,
but I don't think that putting it outside into the sun was said to be a bad thing. Just that acclimating it by finding a semi-shady/semi-sunny spot (out of the mid-day hottest sunlight of the day) for a couple weeks, slowly acclimating it to more sunlight would make for an easier transition for the plant.
Also,as another thought, if it is placed amongst other garden plants, (and watering the garden plants and the nearby soil down with a hose), that will help provide the dappled sunlight AND temporarily bring up the humidity a bit for your plant. (Extra misting is also helpful, however also temporary.) Some people's plants don't have humidity issues it seems, and their plants do fine apparently, so your results will likely vary.
I don't know if others will agree, but I would consider putting it back outside, especially if your other Neps are doing fine with it. Just be sure to place this one in a bit more semi-shaded spot, and perhaps water the surrounding plants and soil to boost the humidity in the area. Then give it time.
The "burn" has already occurred, and the plant will likely take time to recover anyway. It may even show more signs of distress, however from the sound of it, it will recover in time.
When making changes, make them slow and gentle. In the meantime watch the response you get from the plants. They are telling you what they think of the change. But even beneficial change should take place slowly and gently, as plants need time to acclimate and adjust to things, even good things!
[Change is stressful on plants. Small/gentle changes lessen the stress. Large/quick changes increase it.] IMO, that is all you are experiencing with this plant. I learned this lesson repeatedly, as I have "improved" my lighting and growing conditions over the years, and experienced firsthand that even an improvement can harm a plant!
I assume I will be going thru that again too, as we never know what change will be too much, but at least we can try to minimize the stress.
Again,
Take care and good luck!