I have accidentally used Weed'n'Feed on my Buffalo lawn, will it recover

It is difficult to say for sure if your bullalo lawn will recover. All you can do at this stage, if the grass has yellowed and appears dead, is to remove the thatch within the lawn area and allow any of the runners that may still be alive, to run. Applying a product containing seaweed solution such as Yates Yates Dynamic Lifter Liquid Concentrate will encourage root growth, promotes beneficial soil micro-organisms, and enhances recovery in stress conditions. This product can be applied every 1 - 3 weeks. Good luck with the recovery process