Cheryl, who is believed to have split with husband Jean-Bernard (although has never officially confirmed it), was at the event in London to present an award with former X Factor co-star Nick Grimshaw.
However, when hosts Ant and Dec called her to the stage, they simply referred to the star as "Cheryl" while Nick was given his full name...and viewers at home noticed.
Among a flurry of tweets, one fan said: "Notice how Dec awkwardly stopped after 'Nick Grimshaw and Cheryl..' That's another surname that can't be said anymore."
Another said: "Even Ant and Dec don't know Cheryl's surname these days." While one tweeter added: "So did we clock Ant referring to Cheryl as just 'Cheryl' and not that double barrel nonsense? That's all the evidence I need."
Former Girls Aloud star Cheryl turned up to the BRIT Awards in a pale yellow dress and had styled her hair with super-long extensions.
She wasn't wearing a ring on her wedding finger and hasn't been seen with her giant rock for some time.
Although she has't confirmed whether she has split from French businessman Jean-Bernard, it has been reported that Cheryl will keep his surname if they do divorce.
Cheryl's maiden name is Tweedy, and she took Ashley Cole's surname when they married in 2006.
A source told The Sun: "Cheryl has had to reinvent herself several times but her three past names all have very different memories.
"Tweedy is associated with her assault court case, Cole with Ashley's cheating."
The BRITs 2016 red carpet: