Stamped into France

I was reading the thread about not being stamped out of the UK. Well I know you dont need to get stamped out of the UK but what about this....
When I first moved here me and Frank took a coach trip to Paris (never again!!) The driver asked if everyone had UK passports and two of us expressed we had foreign passports. When we approached passport control in France they just let the entire coach pass through. My passport wasnt stamped in to France. I know if you hold a EU passport you dont need a stamp but I hold a US passport. What could of happend if something would have happened to me while in France. For example if I needed medical care or something and they found out I wasnt stamped in? Im guessing its MY repsonsibility to make sure I get stamped but by not being stamped in does/did that make me illegal?

My experience going to France on the ferry is that there's no passport control on the way in-I can't think of a time that I got stamped.  Just drove off the ferry and into France.
I have always been stopped on the way back though.   

I have been to France through a ferry from the UK and also flying in from the US and they never stamp anything!  After we got off the boat, we got into a bus, and there were all kinds of people and the French police got on the bus and just asked a question to the bus driver and left.  It was weird. 

The French are lazy and don't care. 

lol