The site came to the public's attention on Sunday after news of the feature was leaked to the tech press, according to news reports.
A Facebook engineer who claimed to have designed the feature said in a message to the blog TechCrunch that it could be used to quickly look up and "friend" someone who you'd met in person.
"For me, the ideal use case for this product is the one where when you're out with a group of people whom you've recently met and want to stay in contact with," that developer, Ryan Patterson, wrote. "Facebook search might be effective, or sharing your vanity addresses or business cards, but this tool provides a really easy way to exchange contact information with multiple people with minimal friction."
Patterson wrote that he developed the app as part of a coding competition, or hackathon.
"Social discovery" apps like Highlight and Glancee, which Facebook recently purchased, already perform similar functions and have not been hit with the same backlash Facebook received.
Facebook says it was "testing" the feature and that it had not become a formal part of the site, despite the fact that it was available online on Monday.
The company had not promoted the feature.