Bloomington-native Lukas Cavar, 19, joined the Caving Club at IU on a "beginner's trip" to Sullivan Cave last Sunday, which is about 10 miles south of Bloomington.
When the forgotten student reached the entrance of the cave he found it was padlocked shut. With no cellphone signal, Cavar could only scream for help in hopes of motorists at a nearby road might hear him.
Cavar said he licked moisture from the walls to quench his thirst during the almost 60 hours he spent locked in without food or water.
He told the student newspaper that he licked moisture off cave walls to stay hydrated and wrote goodbye messages to his family on his mobile phone.
"You could tell they were pretty shaken up", Lukas told the Indiana Daily Student.
"I managed to get some water from the cave walls, by basically licking the moisture off the wall", he told Reuters.
Sixty hours after they unintentionally trapped him, the same members freed Mr Cavar, apologising profusely.
Cavar, of Bloomington, says he's "really glad to be alive" and has no further spelunking plans.
Two club leaders immediately returned to the cave late Tuesday after finding a pile of clothing in a vehicle club members used to travel to the cave two days earlier.
One of the two was an EMT and saved Cavar at about midnight, according to the Daily Student.
"We have a series of rigorous protocols in place that are supposed to prevent situations like this, but they are only effective if followed".
Early on Wednesday, Cavar posted on Facebook, "Just wanted to let everyone know that I'm safe and sound!"
'Just got safeguarded around 30 minutes back.
Cavar's parents, linguistic professors at the school, filed a missing person report with university police when their son failed to return to campus with the club. "We had a failure in our leadership to closely follow all these safety procedures".
Cavar told FOX59 that it's good to be back above ground, and that he has no plans to go caving any time soon.