The Case of the Missing Artifact

In the heart of the bustling city, at the prestigious museum, a valuable ancient artifact has vanished without a trace. Detective Parker is called in to solve the baffling case. The artifact, a priceless golden idol, was last seen in the museum's main exhibition hall. The curator, security guard, tour guide, and janitor were the only individuals with access to the hall. Can you help Detective Parker unravel the mystery and recover the missing artifact?
Clues:
The museum's security system recorded no unauthorized entry or exit from the exhibition hall.
The curator reported seeing the artifact on its pedestal just before closing time.
The security guard checked the surveillance footage and confirmed no one entered the hall after closing.
The tour guide led a group through the exhibition hall earlier in the day, but no one tampered with the artifact during the tour.
The janitor was cleaning the museum's lobby during the time the theft is believed to have occurred.
Suspects:
Curator Alexandra: Responsible for overseeing the artifact's display and security.
Security Guard Michael: In charge of monitoring surveillance cameras and patrolling the museum.
Tour Guide Emily: Conducts tours for museum visitors and occasionally assists with artifact handling.
Janitor Sam: Responsible for cleaning duties throughout the museum, including the lobby and exhibition halls.
Challenge:
Using the provided clues and suspect profiles, deduce which individual had the opportunity and motive to steal the priceless artifact. Consider each suspect's role, alibi, and any inconsistencies in their statements. Once you've analyzed the evidence, reveal the culprit behind the theft and how they carried out the crime.

Curator Alexandra: Although she reported seeing the artifact on its pedestal just before closing time, she is the only individual with direct access to the artifact outside of public viewing hours. As the curator, Alexandra holds the keys to the museum's storage rooms where additional artifacts are kept. It's possible that she staged the theft to sell the artifact for personal gain. Additionally, her keen knowledge of museum security measures could have enabled her to manipulate the surveillance footage or tamper with the security system to create a false alibi.