Sports memorabilia is a multi-billion dollar industry in the US and where there is big money, there are scammers.  

One father thought he hit a homerun when he won an online auction for the jersey of his son's favorite baseball player.

"I was devastated; I bought the jersey for my son to give him as a present. He is a huge A-Rod fan.  And I was told it was fake I felt victimized," said Dan.

Dan doesn't want to show his face or reveal his last name because he still can't believe he lost $3,200 in this scam.  He bought the jersey off a site called Vintagae Authentics. Dan was told he won a jersey A-Rod wore in 1997 with the Mariners.  He quickly learned otherwise.

"There was an event where Alex Rodriquez was signing jerseys and I approached AROD. His representative said it was a fake," he said.

Postal Inspectors investigating Dan's case bought some items from the site, then went to the teams.

"The team looked at the material on the name plates and confirmed it is not the same material used in the jersey - they also looked at the color of the names and the graphics on the jerseys," said Christopher Cizin, US Postal Inspector.

Both the Oakland Athletics and Seattle Mariners confirmed these jerseys were frauds. Inspectors say this is a growing problem, in fact, some people have no idea they have been taken.

"If they receive the item they may have hung it up on the wall and they are happy with their purchase. They never would have known they were a victim," said Cizin.

Dan tried to contact Vintage Authentics, to no avail.

"When I found out it was not an authentic jersey  I contacted the company and asked for my money back - least to say I never got my money back," said Dan.

The owner of Vintage Authentics was arrested and is still awaiting sentencing.  

Meantime, the best advice is to be cautious when buying memorabilia and work with well-known reputable companies.  Also, Inspectors and consumer advocates recommend using credit cards, not debit cards or money orders for online purchases.  It's because credit cards offer dispute rights, making it easier to reverse fraudulent charges.