If someone tries his best to get Matzah for Pesach but, despite his absolute best efforts cannot get it, has he failed to fulfill the mitzvah of eating Matzah on Pesach?
The answer to both question is: yes, he has failed to fulfill the mitzvah — but he is not responsible for it. The rule is that in a case of ohnes (completely not at fault) then you are not responsible.
The Wolf