The Graceland auction fraud scandal has caught the attention of the Federal Bureau of Investigation, with agents allegedly contacting Riley Keough’s camp about a possible probe,RadarOnline.com has learned. This comes after a judge halted the ruling of a foreclosure action on Graceland following accusations that Riley’s late mother, Lisa Marie Presley, used the famous Memphis property as collateral on an alleged $3.8 million unpaid debt. It was later claimed that Lisa Marie never took out a $3.8 million loan. What’s even stranger is that the notary who allegedly witnessed Elvis Presley’s only c…