I have a very special cat who had a horrid start in life (rescue cat from abroad). We imported him when we came back to the UK and he has always been an indoor cat, bar the odd time he'd jump out a window aboard and would be found cowering under a hedge or bush, hiding from strays.
Now, for the last few days, I've had the doors open and he's been coming in and out, albeit slinking. He went out at 10am and still hasn't returned. At what point do I stop thinking ahhhh, how nice, he's exploring and enjoying himself and start thinking SHIT I HAVE LOST THE CAT? I don't even know which direction he went off in as the. Any distracted me 
Help!!