Spoiler: mistakes were made. Thankfully, nothing serious, but I did walk away with a valuable life lesson. This story takes place a couple of months ago when I thought I was being responsible by bringing plenty of Argentinian pesos in cash for my backpacking trip. While card readers are common in many places, it’s still typical to get better prices when paying with cash. Plus, in smaller towns, you can never fully rely on newer technology being available.

Before leaving the U.S., I packed some crisp hundred-dollar bills, intending to exchange them for pesos and hopefully snag a favorable conversion rate. Argentina’s economy is famously volatile, and while I don’t claim to fully understand the complexities of inflation here, I knew that using the unofficial “blue dollar” rate could stretch my budget further. This rate is often higher than the official bank rate and is used for exchanging U.S. dollars, particularly in informal settings.

Exchanging money on the blue market is pretty common, even though it operates outside official financial channels. But, it can be a bit riskier, depending on the location and the people you’re dealing with. In Buenos Aires, travelers often spot exchange workers on Calle Florida, a busy shopping street, shouting “¡Cambio! ¡Cambio!” to attract customers. After talking to other backpackers who’d swapped money there without any issues, I figured I’d give it a shot. One even passed me the contact for an exchange office where he had a good experience. Feeling prepared, I counted my five $100 bills, tucked them safely in my wallet, and headed to the area.

When I reached out to the contact, a woman met me on the street, introduced herself, and led me into an office building. We took an elevator to the sixth floor, walked down a hallway lined with random offices, and entered a small room where a man sat behind a desk.

The woman was friendly and chatty, asking about my trip and how I liked Buenos Aires. A man behind a large desk greeted me warmly, shook my hand, and asked how much I wanted to exchange. We agreed on a good rate—score, I thought—and I started to pull out my money. As I double-checked my bills and handed them over, the woman kept up the small talk, asking about my favorite parts of the city.

The man placed the money in the counting machine. “400,” he said.

Wait, what?

“No, I gave you 500,” I said, my stomach dropping.

He calmly pointed to the machine, which displayed 400, and held up four bills.

“Yes, 400,” the woman chimed in, nodding along.

Confused, I insisted there had been five bills, but they stood their ground, repeatedly showing me the machine’s count. Had the man palmed one of the bills while I was distracted? Or could I have actually miscounted before leaving? I replayed the moment over and over in my head, but no matter how certain I felt, I couldn’t prove it.

After several minutes of arguing, I gave up. Reluctantly, I asked them to exchange the remaining $400—this time triple-counting every bill before handing it over. At least I still got a good rate for what was left I guess…

Looking back, I realize this wasn’t every traveler’s experience, and most people I’ve spoken to have had no issues. But I got unlucky—or maybe I just needed a reminder to stay vigilant. So, what did I learn? Don’t get distracted during money exchanges. Bring someone with you as a second set of eyes. Consider sticking to more secure, well-reviewed locations. And, most importantly, never go back to that office.

In the end, it was “only” $100, and I’m fortunate enough to be okay without it. But next time, I’ll definitely be smarter. Lesson learned.