Filament run out but printer carried on!

Hi, I have a X1 Carbon (With AMS). A couple of months ago when the printer ran out of filament it paused and requested replacement. I was doing a 4 hour print, the filament ran out after about 2 hours but the printer carried on printing in midair! Is there something I’m missing or has one of the updates removed this ability?

For this to happen I think that the filament sensor has to be stuck or you have a clog.

Hi, Thanks for the reply.
I cleaned all the tubing and vacuumed around the head area then tried a little test run. All was OK so I guess you were correct, although where the actual issue was I’m unsure!?
Thanks for your help
Mike