How to avoid unpleasant interruptions during walks?

I was stopped by a couple people who tried to scam me with some fake antique coins (although that's only an assumption on my part). I was honest and helpful until they actually started talking about money, at which point I hastily retreated. After that I felt like ****. Fortunately it was at the beginning of my daily walk, which I sorely needed, but I thought about going back home I was so rotten. And you might think that it's an unlucky exception, but actually I've ever only been stopped by rude or unpleasant people, and never for anything fun or useful. I think part of it is just the way it works, also my social anxiety makes pretty much any interaction with a stranger unpleasant, and maybe it has a bit to do with living in Russia which is notorious for grumpy people in certain circles.

I just started thinking how I'd avoid that crap. Is it better to lie that I'm in a hurry? Or I had this outlandish idea: apologize in a foreign language (which I actually speak, of course), although that seems a bit too extreme if not completely impossible in my state, and I also don't look like a foreigner (if that makes sense). I also feel a lot like stopping walks and hiding at home again... but that is bad for me. However, it's no good if I have to relax after an activity that I was supposed to do to relax.