That's tough to say, as there are a number of things that could have happened which would cause the OS to report a cable unplugged. First of all (I'm asking because I see this all the time where I work), does your laptop have a hardware switch for the wireless card on the chassis somewhere that could have been turned off? This will cause the OS to report an unplugged cable. Second, is the Device Manager still reporting that the wireless card is installed? This might cause your issue as well. Finally, have you tried resetting your router and your wireless settings on the laptop? It might have just lost it's connection/settings, and could easily be fixed by "reconfiguring" the system.
If all seems well, what I would do in your case is the following: connect with the cable to your router and download the latest wireless device drivers for whatever wireless card you're using. Then go into your Device Manager and remove the wireless card from your computer. Next, install the drivers that you just downloaded and see if that brings the thing back to life.