每日吃瓜

So i'm totally new to bonsai, but i purchased a Serissa bonsai thinking it was a beginner plant because it had accidentally been put in the 'beginner bonsai' section. I got it home and started to look up about it and apparantly they are very hard to care for and very easy to kill, especially if you move them.

So far I've moved it from the garden center to my house, then it's going into my office on monday, where it won't be moved from. My office sits at 18°C/64°F all year round and has reasonably bright lights, but the plant will be placed on a desk near-ish (within 2 meters) of a window.

I've got a mister and some gravel for a water tray underneath it. I tried pruning one wayward stem, which had 5 different leaf sections, down to three leaf sections. Overnight the bit where i cut has gone slightly black. I've not watered the plant yet, as the soil was damp when i purchased it, but i have misted the leaves quite a bit. A single leaf had fallen off when i purchased it, which i carefully removed and disposed of.

I just want to know whether it will survive or if my plant is screwed.

It is bad enough trying to keep it alive in a house, but ten times worse in an office where it will be left unwatered for days.
Spraying leaves is not watering. Plants need to be watered when they need it. Placing it that far from light will also not help it needs sunlight so in a window away from heat.
Branches do not go black overnight when cut, stop fussing, it is a living plant.