08/26/2014 AT 09:40 AM EDT
"We Were Us" was the one that almost got away from Keith Urban
Instead, his duet with Miranda Lambert
became a very sweet 16th No. 1 single, celebrated with writers Nicolle Galyon, Jon Nite and Jimmy Robbins at a high-noon Music Row party in Nashville on Monday.
Composed as a duet, the song was first intended for an unnamed female artist, according to Galyon, who said: "We heard through the grapevine that she was kind of looking for a duet for her record, so we kind of wrote it for that, but somehow it made it into Keith's hands before anyone else got to hear it, and that's where it stopped."
Though a few hundred industry friends turned out to toast the song at Nashville's Tippler restaurant, missing from Monday's party were Urban's duet partner and
his real-life partner, wife Nicole Kidman
"Nic is in New York making a movie so she couldn't be here, but she asked me to say hello to everyone," Urban told the crowd. "This song went No. 1 quite some time ago, and we spent a long time trying to get my schedule and Miranda's schedule synced up. We finally had to do [the party] without her."
Lambert did send a warm video message from her bus, saying, "I love this song, I love the writers for writing it, and I love Keith Urban for asking me to be a part of it."
Urban laughed, telling the crowd, "Miranda was a huge part of this song. You listen to every song in different ways. The images in this one got to me immediately, and Miranda's face and voice came to me at the same time. She was the only singer I would do this with."
Urban also noted that unlike many duets, which are often recorded separately, the two singers recorded "We Were Us" at the same time in the same room.
"She and Blake came over one morning, we all hung out for a while and then we went in the studio and recorded it together," he said. "It was so loose and so cool, so special to be there together."
Urban's current single from his album Fuse
is "Somewhere in My Car." Taking a break from the judge's seat on American Idol
, he is currently on the road with his Raise 'Em Up Tour