Bus lanes

Hey,

I went to a city i had never been before and i ended up on a bus lane, wasnt well sign posted and it looked like i could go straight ahead and wenty over a bridge and still looked like a normal road until i came to a traffic light and there it said bus lane!! however there were loads of police on the side of the road all spread out, and they all gave me a what the muck u doing look and as i waited at the traffic lights, no-one came over but i saw one bloke who took pen and pad out and started writing, i am not sure whether he was writing my reg plate down or not, if so could i still get fined? there were no camera bus lanes though i dont think so anyway.