Mazda Repair: Mazda Protege brake drum failure, brake drums, wheel cylinder

Question
Is there a way to identify a catastrophic failure without removing brake drum cover, and is saturating the brake assembly a normal failure mode?
   Here's the background on my question...When I had my tires rotated last weekend, the service manager there told me my rear wheel cylinder had failed and that my car was quite dangerous to drive.  Of course, both sides then needed new brakes.  I told them I had just had my brakes checked two weeks earlier at Brakes Plus, to which the service manager replied I should talk with Brakes Plus for not catching this problem. He took me into the bay to show me my brake drums: the entire assembly was soaked with brake fluid (wheel cylinder, pads, cover, everything, as though high pressure fluid had been sprayed throughout the drum, and added that it was a safety and fire hazard for me not to fix them immediately.  They said it had obviously been there a while. I don't understand how when I saw my brakes at Brakes Plus, they were clean with not even a drip of fluid. I didn't even have a loss of brake pressure or any drips under my car, so the expensive news (well over $400 to repair)came as a huge shock. Thank you in advance for helping me understand the problem and how to forsee it in the future!

Answer
it is possible that they could of looked ok however you may of had a weak seal or line that just wasn't noticed with a visual check, when the pads get soaked with fuild they are no longer any good and have to be replaced. 400.00 bucks is a normal price for a complete brake job if they had to change everything.