What to do with baby bunny

[Sneaky2006]

My husband found a baby bunny outside laying under the jack for his car! He brought it in to me and I thought wild bunnies (if there is such a thing) can't live inside? So thinking it was okay, I let it go outside and now 3 hours later it was sitting on the windowsill to our basement window. This is very odd because every single bunny we've ever seen outside has taken off running with the slightest movement. I don't know if it's sick or hurt, or if it's just that young... will the mother ever come back now that we touched it?

My mom always used to tell me that wild bunnies would tear their hair out if we caught one... although she could've just said that so we wouldn't
Now what do I do?
Here's a pic!