The rumored couple has displayed a lot of PDA in recent days, starting in Miami on Thursday night. A source tells ET that Richie and Scott were "affectionate" at LIV nightclub at the Fontainebleau, where Disick was also hanging out with Travis Scott and Jonathan Cheban. The source said Richie sat next to Scott in the DJ booth the whole time she was there, and that the two were "whispering to each other and laughing."
On Saturday, they were snapped taking a stroll on the beach in Miami.
Then they partied on a boat with friends, singing Phil Collins' "In the Air Tonight."
On that same boat, photographers snapped this shot of Disick's hand on Richie's bottom, as the two held each other close.
Then came the mystery congratulations. At Seaspice restaurant, the pair received a fancy dessert with the message, "Congratulations Scott and Sophia" written on it. [Note: Sofia's name is misspelled on the plate.]
The two shared multiple kisses at the table, as the food was delivered and accompanied by sparklers -- what the congratulations are for remains unclear.
Richie and Disick have dismissed rumors of their relationship as far back as May, when they were first spotted together in Cannes. The 19-year-old model swiftly tweeted about the supposed romance, saying, "Scott and I are just homies."
She denied the speculation again in June, after she was spotted walking arm in arm with the reality star, tweeting, "The last time I'm gonna say it. Scott and I are just friends. I'm single and focused on friends, family and work."