The reason? The bad boy crooner had a secret rendezvous with ex-wife Miranda Lambert and poured out his heart about how much he missed her, friends revealed.
The 40-year-old mentor from NBC's hit talent competition The Voice got cozy with his ex during a Nashville gala while Stefani, 46, was thousands of miles away in L.A. Lambert's boyfriend, Anderson East, was nowhere to be seen either, insiders said.
"Gwen has always been insecure and jealous over Blake's womanizing ways, but she's going to be crushed when she learns he and Miranda are getting chummy again," said an insider.
Even worse, Shelton lied to Stefani, saying "he avoided Miranda and didn't speak to her" at the Nashville shindig.
But the sweet-talking love cheat cornered Lambert backstage and "complimented her on her newest song, 'Vice,' said she looked amazing and asked to have a private word with her," confided the source. "Blake said he's been carrying around a ton of emotional baggage and guilt since they divorced last summer."
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"He told her he regretted how their split became so nasty, and even suggested he wished their marriage could have worked out. He also told Miranda he misses her!"
Stefani will take this stuff hard, the source insisted — especially since, as RadarOnline.com reported, the songstress already been stabbed in the back by musician Gavin Rossdale, who she divorced after 13 years of marriage and three sons, amid charges he was cheating.
"Blake and Miranda reconnecting could be the nail in the coffin for Blake's relationship with Gwen."
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