Over the weekend, the cast of Vanderpump Rules traveled to Las Vegas to celebrate the birthday of Tom Schwartz. However, not everyone was in attendance.

Stassi Schroeder Continues To Hang With Kristen Doute Amid 'Vanderpump Rules' Filming

Although several of Schwartz's Bravo co-stars, including Scheana Marie Shay, Jax Taylor, Tom Sandoval, Ariana Madix, Brittany Cartwright and Katie Maloney, made the trip, Kristen Doute was noticeably absent. On Twitter, after a fan questioned Doute about her absence, she explained why she was not present.

Kristen Doute Refutes Relationship Reports, Even After Re-Tweeting News Of Her 'New Man'

Although Doute was unable to attend Schwartz's birthday festivities, she did send her co-star a birthday message on Saturday.

While it is unclear what exactly happend to Doute that led to her facial fractures, she previously told fans she would soon be going under the knife as a result.

For more Kristen Doute, tune into Vanderpump Rules season four, when it premieres on Bravo on Monday, Nov. 2, at 9 p.m., and check out the trailer below. During the upcoming season, fans will watch as Doute's relationship with James Kennedy comes to a messy end -- with the help of new girl Lala Kent.

Tags: kristen doute Tom Schwartz vanderpump rules Bravo Reality TV