Spencer Pratt literally fled his Pacific Palisades home before it burned down with just the shirt off his back ... which is evident from the new video obtained by TMZ.

Spencer was at Marshall's in Santa Barbara Sunday, wearing the same shirt he was wearing last Tuesday when the massive fire erupted in his neighborhood, torching the family house he shares with his wife, Heidi Montag, and their 2 kids.

Spencer and Heidi lost everything in the fire, and he's already moving to rebuild their lives. He's trying to get Hulu to do a show with his family, which will help with the enormous cost of rebuilding and restoring.

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Pratt went on TikTok Friday and implored his fans to watch the video, explaining if enough people clicked, he'd score $1,100.

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The one sliver of a silver lining ... Heidi's 2010 song, "Superficial," is sitting at #1 on iTunes ... with a little help from Flava Flav and Emily Ratajkowski. The song beat out Bad Bunny's "Debi Tirar Mas Fotos."