Austin scored his third goal in three games to cancel out Ryan Fraser's opener and secure Saints a 1-1 draw at the Vitality Stadium.
After slotting home Nathan Redmond's cross, Austin celebrated in front of the home supporters, who had been jeering him throughout the game.
Austin spent six weeks training with Bournemouth when he belonged to Poole Town back in 2009, but the move was blocked as the Cherries were then placed under a transfer embargo.
"Their reaction was a bit odd, I am not too sure why. It was not my fault," said Austin, who joined Swindon instead and then Burnley.
"If anything, I was going to sign here and (manager) Eddie (Howe) and (assistant manager) Jason (Tindall) did everything they could to sign me and I would have signed.
"But, like Eddie said earlier in the week, he could not stand in my way and I am forever grateful to them for letting me go and giving me a chance.
"It is not strange to score against them. It was a long time ago and I never actually signed for the club."