Your seedling (because that's what it is) hasn't been hardened properly and is now heavily stressed.
I am not overtly familiar with Miracle berries, but like baobab and other exotics a few pop up now and then and they are usually tiny and don't appear to have been hardened properly.
The hardening process in these exotics, when grown outside their native areas, is to expose them slowly to the different growing conditions so they can adapt. For example in high moisture plants like this one they should be covered with either a clear plastic bag or a glass jar to keep high levels of air moisture and be progressively exposed to our drier climates, with regular misting providing high levels of moisture.
Light is another factor: standard practice is to grow these seedlings inside and in indirect light until they are large enough, then they can be progressively exposed to direct sunlight, all the while providing them with adequate levels of moisture.
Finally what you did. Snake o..., I mean neem oil + direct sunlight often results in leaf scorch. We've seen several cases on this board over the past 4-5 months.
You uprooted it, meaning you stressed it and damaged its tiny roots. That's why it wilted when left in the sun.
What you should do not? I advise you find a nice spot inside the house with plenty of indirect light and put your seedling there. Put a clear plastic bag over it to keep moisture levels high and remove it once a day to wipe the excess moisture and to avoid algal growths.
Do nothing else: allow the seedling to recover and rebuild its strength then, if it survives, you can start the hardening process anew.
