you were going door to door for what you thought was God .. you ended up at the door of someone who was praying to God ...for someone to come to his door..
You were not there for God but, but a book publishing company.. so no prayer was answered...
let me bottom line it for you .. you were going door to door .. chances are pretty good that some one might have prayed before you got there..
It happened to me more than once in my fields service experience..
you go to enough doors something will end up seeming intentional ,
it would be odd if that scenario never happened .. what are the odds of going door to door looking for people looking for God and you never found ONE.. very slim
hope that puts it into perspective .. it is what is .. not divine intervention