C510 sudden "insert sim".. Emergency!!!

So, I literally left my phone on the side of the sofa as I lay there and watched tv, looked at it to check the time, then looked again, and suddenly is said "inactive sim".. Hadn't even touched the phone! It wasn't on silent yet didn't even make a sound.. Now, when I turn it on it says "please insert sim card or view the demo".. No matter what I do. I am away from home and don't have access to a cable to plug the phone into my laptop.. I can try buy one early tomorrow but if there is something else I can do please someone tell me..

I need this phone desperately as I am returning home tomorrow and need to be in contact with my parents so they know when to pick me up. Without the phone, I don't have any numbers.. :(

Someone please help.. I have unlocked the phone myself with a2uploader and updated it with SEUS before..

Why has it just suddenly done this? It hasn't been dropped or anything it was completely random.. :(

Please help.. :(