Unfortunately this is the the almost inevitable fate of Junipers that are kept indoors. This forum is littered with the corpses of Junipers that were purchased on a whim or given as gifts. Vendors make it seem that keeping these trees is simply a matter of watering. The truth is that Junipers are one of the worst choices for indoor bonsai. They can look good while they are slowly dying, just like a Christmas tree. By the time they are dry and brown they are already in distress.
Since you have no options available to you I have little hope it will recover. If you wish to grow inside there are other, more appropriate, species. Without a decent window or supplemental lighting of some sort I'm afraid you are fighting an uphill battle. There are precious few trees that will do well inside under low light conditions. You might try a Schefflera.