My "oh sh*t" moment of today.
Near the end of our walk we called in at the co-op. Its part of a very small mall of maybe 10 shops and is tucked into the far right corner (that bit is important).
From our walk it meant us approaching from the left and when we got to the door we walked straight in. We followed the arrows etc and completed our shop BUT when we exited, going the opposite direction was a queue of 20+ people

.
It was then we noticed the sign "one out, one in"
Coming from the left we had not seen the queue or the sign and walked straight in.
Heads down we scarpered as quickly as possible.
A wonder we weren't lynched.