I read this post just before we left for Galapagos. We planned to stay about four days in Quito on the way, so I warned my friends about this “smelly liquid” scam, and potential pickpockets in general.
We were walking down a busy street in Quito returning to our hotel after shopping at a street market. Suddenly I felt a liquid hit my back, and I thought I’d been nailed by a bird. My two companions were hit too. An elderly-looking couple (perhaps a disguise) quickly approached us with paper napkins in their hands. Then I remembered the warning from peeweediver from his post in this thread. I shouted out to my companions to beware of this scam, and the elderly couple quickly disappeared! Luckily, we avoided being victimized.
Examining our clothing later we found a thick green fluid with a vinegar aroma. It washed out easily and completely with a little soap and water.
We had a few good laughs about our experience later. We went on to have an amazing week of liveaboard diving around the Galapagos Islands.
Thank you, peeweediver, for your informative post. It was astounding good fortune to have read it, and it prevented us from falling for this scam.