Spurs confirmed that a deal with Internacional for the Brazil international had been agreed back in March for a fee reportedly in the region of £8million.
It was also announced that the 21-year-old would join the North London club following the end of the Copa Libertadores, which finished on 18th August.
Internacional claimed the 2010 Copa Libertadores with a 5-3 aggregate win against Mexico's Chivas Guadalajara and the midfielder was expected to show up in London last week, but Redknapp is still awaiting his arrival.
The exasperated Redknapp told The People: "Have we really signed him - or is he just a myth?
"I've never seen him here. He's supposed to be here...but not today!"
Sandro is due to join up with the Brazil squad of European-based players in a training camp from September 2-8 and Redknapp added: "I know he's meeting up with the Brazil squad next week and train in Spain.
"I might have to go to Barcelona for three or four days to watch him - maybe I'll take the wife!"