I have put my extra student loan money in savings along with extra pay, so I can't say my surgery was paid for by just that, but I also can't say it wasn't since it all went into the same account. Kinda a stupid answer I know, but I just put money into the account, I don't keep track of every penny that goes in. I was lucky enough to get vacation pay while working another job that paid decently, so the extra paychecks were put into savings to help build it up.
Even now I put extra in savings since it is not very much. I normally take a few months off in the fall, and that money helps make the payments back until I restart classes since I don't budget my student loans in my month bills while I am taking classes.
I have no idea if people have done it before, but odds are some folks have.