Phineas Gage style indeed (is that a precursor to Gangnam style?) - ironically (referring to one large iron rod), Phineas Gage's accident is believed to have entirely removed his OFC, as well as parts of his PFC. Though Gage likely suffered some mental changes, his recovery was a far cry from any sweeping "lose his decision-making ability entirely" diagnosis, even with injuries more extensive than just the OFC, so I think we can safely rule out the statement above without resorting to unethical experimentation.
This misconception may have originated with Antonio Damasio:
Antonio Damasio, in support of his somatic marker hypothesis (relating
decision-making to emotions and their biological underpinnings), draws
parallels between behaviors he ascribes to Gage and those of modern
patients with damage to the orbitofrontal cortex and amygdala. But
Damasio's depiction of Gage has been severely criticized ...
In neuroscience, this type of error is called a "reverse inference". For example, if we find that a particular region of the brain is active when subjects experience an "emotion", we can't then conclude that it always means subjects are experiencing that "emotion" when it is active. That brain region may have other functions besides that emotion, many other brain regions may be involved in experiencing that emotion, and different regions may be involved in different contexts.
Furthermore, in modern emotion traditions, the distinction between emotion and cognition in general tends to be blurry, to the extent that some popular emotion models argue that the two cannot feasibly be separated. In other words, depending on your preferred model, "emotion" may refer to all cognition (the entire brain), so the answer to your question would be ... yes?
Note: I don't know anything about Jonah Lehrer's book, but Wikipedia says:
On March 1, 2013, following revelations that Lehrer has been caught in
numerous falsifications in his œuvre of writings, Houghton Mifflin
Harcourt announced the book was taken "off sale" after an internal