Jake Haro -- accused, along with his wife, of killing their infant child -- is lending a hand to cops searching mountains outside L.A. for the missing baby, but so far they're still coming up empty.

San Bernardino County Sheriff's deputies escorted Haro Sunday in an orange jumpsuit and shackles to a mountainous area of Moreno Valley in Riverside County, CA ... hoping to find 7-month-old Emmanue l . RMG News

Haro and the cops conducted their search for several hours in the afternoon -- and while it ended unsuccessfully ... there was a brief moment of hope, fueled by a false report.

Check out video posted to TikTok, which shows an amateur journalist reporting from the scene -- he mistakenly says the body was recovered as deputies lead a shackled Haro to a police vehicle and s

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