Where is the guard at the museum on Counterfeit island?
There is a museum security guard at the entrance. You cannot enter until you have taken the Underground tour. Later, you will see another guard in the Security Room. When the first guard is missing, he is at the clown store.
To get the museum to let you in on Counterfeit Island, you have to go through the Underground Tunnel, then exit the tunnel, where it leads you to the City Docks. There will be a man waiting near the exit and he'll tell you to get a job at the museum, then meet him at night. You go to the museum and tell the guard you're there to apply for the job. He'll let you…
The red-haired guard you meet at the Museum is at the Clown Store after the painting is stolen. The female guard is in the Security Room. Slip past her at night to enter the museum. The next day, get the timecard from the guy guard (at the Clown Store) and take it to the Security Room in the museum.