Nick Cannon Impostor Pulls Off Jewelry Heist

People in Nick Cannon's life have a problem with Glitter ... someone pretended to be part of Nick's posse and stole thousands of dollars worth of jewelry from Fred Segal.

Here's what happened. A guy who called himself Michael called the Santa Monica store and said he worked for Nick, and, being the hubby of Mariah Carey, he needed some jewelry STAT.

Michael asked the woman from Fred Segal to meet him at the Roosevelt Hotel in Hollywood with the goods. The woman obliged, put the jewelry in a bag and drove to the Hotel.

A guy met the woman at the front door, but it wasn't Michael ... it was a guy claiming to be a security guard and dressed like one. The guy apparently indicated he would take the goods up to Nick's room and come down with cash -- in order to avoid paying taxes.

You guessed it. The woman gave the dude the goods and that was the last she saw of anyone.

The LAPD is on the case.

As for how much the jewelry is worth, let's put it this way. You can't buy a pair of pants at that store for less than $300.