A challenge, if you will dear reader. Go out, it doesn't really matter where but to a place you don't really know. A piece of your local town, a forest you've never been in, a complicated road system, and become lost.
I recommend doing so at a speed that is faster than walking. As the faster you move the more concentration it takes, and it will be more difficult to get lost the slower you move. The more time you have to take in what's around you the more time you have to remember the way back.
Now "lost" and "stranded" are two different things, and so I recommend you take your necessary precautions. And while I don't have an issue with you bringing your phone, it better be off the whole time. The goal is to get into a flow of movement without hesitation in an unknown space, choosing the path less travelled and to never stop to make a decision. Getting lost takes time, so don't expect that 30min be enough time, schedule your being "lost" with ample time.