The Tottenham striker was introduced as a substitute at St James' Park and put Spurs 2-1 up before Shola Ameobi secured a 2-2 draw for the Magpies with a late equaliser.
Redknapp was asked after the game if he had seen the Tweet - confirmed by a Tottenham official to come from a fake account - which stated Defoe would start Sunday's clash but it is clearly a world in which he has no interest.
"I didn't see the twit, the tweet, because I can't work a tweeter," Redknapp said.
"I don't know what it is. I haven't got a clue what a Tweet is.
"It's beyond me all this Tweeting and Facebooking. I don't understand it as I live in another world to that so I don't know if he's Tweeted or not.
"In fact I couldn't care if he did or he didn't really.
"We used to talk to each other at one time and now we talk on computers and all that. I don't know what the world's coming to really."
Redknapp later joked during his press conference that Defoe was unsuccessfully trying to contact him on his phone.
"This phone don't even work. The ringer's broke. It's Jermain Defoe - 'Why didn't I 'effing play' - what's he Tweeting me for?"