Shock!
My background with plants is just a bit of gardening around the house and a few potted plants inside at various times, for a couple years when I was 18 I worked in the Home Garden Department at Home Depot and I ran into alot of things.
When repotting plants, which is generally recommended once a year, always to the next size up... you have to be careful or you can dmg roots.
Damaged roots lead to shock. Other reason's that can cause this are moving a potted plant to a new location, with different amounts or intensities of light.
Plants CAN recover from this state. Such as the hibiscus I currently have in my cham's cage. After I repotted the hibiscus, and moved it into the cage, leaves started to drop off. It looked almost dead with a few tiny green bumps coming up out of the branches. Just kept taking care of it like normal, letting it dry out in between watterings then soaking the soil completely. Now it's about back to where it was when I bought it, had a couple flower buds come up (that Evo broke off climbing around on it) and it's been a slow recovery over the last month but it's doing well.
Had this happen before with a habanero chile plant I kept indoors under a grow light, several times with that plant when I would repot it or tryed to use a window and eventually outside. With this plant the leaves would actually grow different depending on the light conditions. Larger, thinner, and less numerous leaves under the soft glow light, spreading to take advantage of every photon. Outside smaller, thicker, more compact leaves outside (maybe about 1/4 -1/2 the size from under the growlight) seemed more advantageous for the plant as the sun moved throughout the day rather than 1 specific angle.
Anyways, hope this helps. Just keep taking care of it as best as you can and it should grow. If there isn't alot of light by the window you may consider addind a grow bulb spotlight, obtainable for about $6 here at home depot, or available as a florescent for a bit more in various forms.