Realise you're going the wrong way? Just take your phone out as if you're answering a text, look at it for a few seconds, then put it back in your pocket while shaking your head disapprovingly before heading back where you came from. People don't question what isn't their business.

The hard part is finding a way to do it in which you don't look like a lost idiot because you just stopped, turned 180, and walked back the way you just came from.