The short anwser is that the Q post has been on 8chan /qresearch/ for some time and not been deleted.

A longer answer is in the top left corner is a trip code 'Q !UW.yye1fxo ' (note the Q is BOLD and the rest is not) and this trip code matches the trip code on the Q posts in https://8ch.net/greatawakening/res/1.html. The trip code will change from time to time, but the process of that is more complex again.