Got a HTC One X yesterday and opened up the sim card tray with the little metal tool to see how it worked. The holder with sim card in the popped out.

Replaced it but phone showed no sim card error.

Opened tray again and it comes out empty so the sim card itself is stuck inside the phone.

Any ideas how to retrieve it ?

 

Forget that - turns out sim had dropped on floor !! Sort of explains why phone couldn't find it...