Why is there a spider in my bathroom and why does it not move at all?

If you blow on it or its web or spray it with water, and it doesn't move a leg, it is probably dead. You have the right idea to dustbust it. If you don't know anything about spiders, suck it in and empty the dustbuster OUTSIDE just in case it IS alive. If you have some oven mitts or silicone gloves, wear them and you won't be so afraid. If you have some bug spray, spray that and you will be SURE it will be dead.