On the video of the theft, you can see that it was the "shady guy" who set you up. He is the henchman of the notorious Black Widow, who is posing as the Chief Inspector!
(see related question)
you have to catch a thief on counterfeit island and when you catch the thief you will get a medallion
In Counterfeit island, you chase him.
Click PRINT.
The art thief is back on Counterfeit Island. As part of Counterfeit island, you don't need to do anything in Early Poptropica except get the key from the curator at the Pop Art Museum, then return to Counterfeit Island to open the Inspector's house.
Night
night right after you get caught the thief is the investigator
the mimes do he's at the music place
He is in the clown store.
hang from the light above it
Go back the museum : you have a package waiting for you.
Go back the museum : you have a package waiting for you.
She warns you that there is a notorious thief at work on Counterfeit Island, and gives you the key to the Inspector's house in the Country Side.