Your prayer to God through Jesus is never in vain. God hears all prayers, and answers them all according to the faith of the individual person who is praying. He also answers according to His love.

When Jesus fed the 5000, and later the 4000, He didn't start with nothing. Rather, He started with a small amount of bread and fish, and multiplied it to feed the whole groups. Why did He start with something rather than start from noting? He could have started with nothing; He is that powerful.

He did it because of the weak faith of both the disciples and also the people. Starting with something built their faith, because they could see that there was something there... rather than simply popping the bread and fish into existence with nothing to start with at all.

After all, if you want a new car, is your faith strong enough to simply pop it into existence in your driveway? Probably not. But if you work for it - get the money and pay for it - your faith is strong enough to do it this way. You have done it before, or you have seen other people do it, so you have faith that you can do it, too.