In the old photo, a shirtless Rob chows down on a sandwich on a beach in Malibu, with his tattoo sleeve on display as he wears a black beanie.
"#tbt Me just chill-zoning in Malibu eating a pulled pork sandwich," the 28-year-old captioned the snap, complete with a few emojis.
While Rob has been known for deleting all of his social media activity shortly after posting it, so far, the picture remains online.
Despite being a member of the Keeping Up with the Kardashians clan, Rob hasn't appeared on the reality show in a while, secluding himself after gaining weight and battling depression, sources have told PEOPLE.
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In her recent interview with Complex magazine, sister Khloé Kardashian, 31, detailed the close relationship she has with Rob, who lives with her.
"Rob lives with me now and I wouldn't have it any other way. I love having him with me," she told the magazine. "He's going through a hard time now, and it's behind gates. With this crazy lifestyle you have to think of places where you can still have your freedom."