I went without underwear

This is not a terribly new story, but let's use this one to refill my much too empty posts section:

During the summer months, we often went to one a few nearby lakes by bicycle. I usually slipped into my bikini at home and put some dress or a top and shorts on top, so that I could quickly jump into the water once we arrived. This time around, right after we had been out of the water for the second time, someone suggested to ride back to the city to get some icecream and maybe do some shopping. Everyone was okay and started to change from their wet swimwear. When I rummaged through my bag, I realized to my chagrin that I had forgotten to pack my panties. I was unsure what to do now. I definitely did not want to tell the others about it, and I also did not want to go wearing my wet bikini bottoms - they would only soak my skirt or even worse get me a cystitis; waiting for them to dry was not an option either as everyone else was about ready to leave. I finally took a deep breath and decided that I had to go without panties beneath my skirt, I just had to be careful. As a first measure to not rouse any suspicion, I began to change clothes under my towel and pretended to put on some panties.
A short while later, we were cycling back to the city, me very aware that I was only wearing a jeans skirt with nothing beneath as the wind rushed by. After buying icecream cones in the city, we went to some large sun-bathed stairs to sit and enjoy our icecream cones. I was careful to keep my legs closed while we ate and talked. I started to relax a bit as I managed to cover my private parts well beneath the skirt. Next, we went to a nearby mall. I went up the stairs with the girls, as the guys wanted to take a look at something on the first floor. I heard a cough by one of them but didn't think about it at that time. After we visited some stores, we went outside again, after buying some beverages at Starbucks. We again went to the stairs. I noticed that the one guy who was coughing earlier was sitting beneath me on the stairs looking up. Only then did I realize that I had not closed my legs and he was staring right between them. I quickly closed them, turning bright red and gave him a stare. He gave me a satisfied nod with a smirk which only mad me turn even more red. The rest of the day I tried to take care to not giving him another opportunity to glimpse between my legs - and I hope I managed. But needless to say, that at some later time, he did an another view and more.

And for your imagination, this is the skirt in question:
https://www.imagebam.com/view/GA6KN4