My phone cannot search the carrier.

I recently took off the front display on My iPhone 3gs, and cleaned it up by my self. When I finished cleaning it, it looks perfect. But not until a while i found out the phone isn't connected to any mobile carrier. I tried to search manually, but it pop-up a window and say it can't search, i also tired pulling the sim card out and putting it back in, it still didn't work. and now I'm wondering did I brake the antenna while I'm removing the front cover.

Is there any way I can get it back to normal? how can i check is the antenna broken or not?