Whodunit? Austin Theory.
WWE solved the case of Vince McMahon's missing Cleopatra egg on last night's episode of Raw, with authority figures Sonya Deville and Adam Pearce assisting the hunt before SmackDown's Sami Zayn, of all people, revealed Theory as the thief.
The terms set out by McMahon dictated that whoever found the £100 million egg would get a WWE Title shot. This should, technically, have been Zayn, though Vince decided to give it to the "brash but talented" Theory instead. From there, Austin ended up wrestling Big E for the gold in the main event, falling to a Big Ending and subsequent pinfall after a distraction from Kevin Owens and Seth Rollins, who were arguing at ringside.
The missing egg storyline was part of WWE's heavy promotion for Red Notice, the new Netflix movie starring Gal Gadot, Ryan Reynolds, and Dwayne 'The Rock' Johnson. This was originally put together with a Survivor Series appearance from Johnson in mind, though financial obligations meant WWE had to continue even after learning that Rocky couldn't be involved.
McMahon claimed at Survivor Series that Rock had gifted him the egg. Theory explained on Raw that he got carried away while trying to take a selfie with it, so he took it.