One time I got taken was in an airport hotel parking lot in Tampa several years back. It was night, I'm going to get in the car and a guy comes up to me with a crock and bull story about his Mercedes breaking down around the corner, with his family in it yada, yada. yada. I could have gone to get in the car, but as I was alone and who knows if he is a druggie with a weapon.
We looked at each other and we both new the whole thing was horse hocky, but I opened my wallet open, gave him the $22 bucks in it, wish him all the best of luck and zip in to the car while he is still fondling the bills.
I make it a point to have a bit of cash in my wallet, and if I have more, stash it somewhere else on my person. $20-$30 is credible, an empty wallet could result in more of a shake down if you are getting robbed.
I was helping organize a sports tournament with a couple of hundred people, and later in the week a person was robbed of $600 in the same parking lot.