Married at First Sight's Andrew is sharing why he thinks his bride ran away.

Andrew and Lauren’s wedding on last night’s episode of Married at First Sight appeared seamless – well, as seamless as a wedding can be when the bride and groom have never met.

The only ‘hiccups’ being: Lauren was nervous about telling Andrew of her 11-year-old son. Oh, and she was looking for someone taller.

But now, Lauren, 33, has done a runner and Andrew has no idea where things went so wrong wrong.

“I don’t feel like I did anything wrong on the night,” the 38-year-old told TheFIX. “We both had a really good time.”

He's been left guessing at reasons:

"I do think I’m probably not the ideal look of the person that she expected," he said. "She does like tall guys. I go between 5-foot-11-and-three-quarters and 6-foot. In heels, she would tower over me."

The pair made it through the ceremony and reception just fine. They said their 'vows' at Wylies Bath in Coogee, Sydney. And they met each other's friends and family.

"My first reaction was good," Andrew told TheFIX. "I was attracted. She was quite tall. She had a bubbly giggle. It was the ideal situation for me to turn around and see her like that. And her dad was pleasant too."

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But then.... Then she disappeared while the pair were having post-reception drinks at a venue near their hotel.

"I turned around and Lauren had vanished," Andrew tells the cameras as he wakes up in an empty room the next morning. "She was gone."

The single mum left all her possessions in the hotel room, including her wedding dress. She did not give Andrew any warning of her departure.

This is a first for the Channel 9 match-making series. No bride has ever given up, without warning, only hours in.