I don't think you broke anything. I found this ebay listing so you can see what the part looks like:

http://www.ebay.com/itm/e46-Front-St...p2047675.l2557

Those are just splined studs that are pressed in to the shock mount. I found this on a Google image search so you can see what one looks like:

http://www.evocorse.com/en/colonnett...aggio-435.html

In the picture of your car it looks like the stud is pretty far down in the bolt so I think as you were loosening it it pushed itself down until the splines were out of the mount and then it just spins. With the tire off you should be able to get a long screwdriver up in there and tap it up so the splined part is back in the mount. To do this safely though you're going to have to get it up on a jack stand.

William.