The World Anti-Doping Agency (WADA) says the electronic account that shows Yulia Stepanova's location has been hacked.
The 800-meter runner is in hiding after helping to expose Russian state-sponsored doping.
WADA’s electronic system ADAMS allows athletes to enter information about their whereabouts to help the agency coordinate testing.
The anti-doping body said on August 13 that Stepanova's account on ADAMS had been accessed by someone other than the athlete.
"WADA is in contact with the relevant law enforcement authorities," a statement said.
Stepanova and her husband, Vitaly, a former Russian anti-doping official, left Russia after giving evidence of the extent of Russia's state-sanctioned doping program and cover-ups.
They are currently living in an undisclosed location.
As a result of Russia’s doping scandal, the country’s track-and-field team has been banned from the Rio Olympics while all Russian competitors in other sports had to prove they were clean by meeting several criteria in order to be eligible to compete at the Games.
WADA Account Of Russian Whistle-Blower Hacked