A Song No One Remembered. A Podcast That’s Hard to Forget.

On “Reply All,” the hosts PJ Vogt and Alex Goldman explore all that’s “delicious and weird” about life in the internet age. It seemed like the most minor of mysteries, the kind a friend or spouse might indulge before gently changing the subject: A man who can’t remember the name or artist of a favorite song from his youth struggles to find either online. But the closer PJ Vogt looked at the case (Could a person remember a song that never existed? ), the deeper he sank into a mind-bending rabbit hole.

What lay at the bottom — past detours into the nature of obsession, the science of memory and the forgotten history of 1990s alt-rock — is the subject of a recent viral episode of “Reply All,” a popular podcast hosted by Vogt and Alex Goldman, that the Guardian called “perhaps the best-ever episode of any podcast. ” Vogt, 34, and Goldman, 40, have made a specialty of exploring the strange and ineffable experience of life in the internet age. When they started the podcast in 2014 — adapted from their earlier New York public radio show, “TLDR” — it was sometimes described as being about the internet, a simplistic characterization that reflected the relative innocence of the time as much as the self-consciously nerdy sensibilities of the hosts. But in more recent years, as increasingly ambitious episodes have taken listeners inside telephone scam rings in India and to a maximum-security prison in Illinois, the show has become much harder to pin down.

It’s also found a growing audience. Since the release of the forgotten-rock-song episode, “The Case of the Missing Hit,” on March 5, the number of overall listeners to the show is up 35 percent across platforms, according to a spokeswoman for Spotify, the owner of Gimlet Media, which produces “Reply All. ” (The company doesn’t release listenership data for individual episodes. ) I spoke to Vogt and Goldman about their work and making “The Case of the Missing Hit,” which involved a trip to Los Angeles to record a new version of the song, a Hail Mary call to the former Barenaked Ladies frontman Steven Page and an abandoned foray into the many-worlds hypothesis of quantum mechanics.

These are edited (and spoiler-free) excerpts from the conversation. This story started with an email from a listener named Tyler. What made you think it should be an episode of “Reply All”? PJ VOGT I think Alex and I both get really frustrated when something should be solvable and it’s not, or when it upsets our idea about how the world should work.