A/T disengage switches are on either side of the thrust levers. Pressing TOGA will re-engage the A/T as will selecting the A/T switch on the MCP or selecting FLCH.
TOGA after a bounce will not re-engage A/T as the switches are inhibited for 5 secs. If A/T is off then the pilot has manual thrust control, if A/T is active then the thrust will be being commanded to idle. If you push the throttles forward and release them A/T will command them back to idle again!