Does Hard Work Really Pay off?

I'm pissed.
Last week my landlord's secretary called me and said they never received March's rent. The first thing I do when I get paid at the end of the month is go to my job and buy a money order for $425 to pay my rent. Since I work at the post office, I cancel my mail with my own two hands and send it on it's way to prevent it from being lost. So one of two things happened:
A) The mail carrier put it in the wrong mailbox.
B) The secretary is lying and trying to scam me.
I never had a problem with his secretary and she is very nice, so I know that it's "A".
Since I can't find the receipt to my money order, they have no way to track it, and therefore no proof that I mailed it. I told them that I have it on my bank statement but she said that's not enough evidence.
I have to repay the $425 and to do so I had to drop my summer class so I can get a refund to pay this rent again. $850 out the window over something that's not my fault. Because of this, I can't even go to school. I work hard to pay all my bills on time. I've never been late on anything...cable, gas, electric, rent, school, nothing. Everything I work hard for is falling apart. I know some will say "It's not the end of the world." But when you're a college student, living on your own, working hard to keep your bills paid on time, it is.

So my question is: Does hard work really pay off?
Of course is does, just not for me. Fuck my life.