My 24-Speed Became a 3-Speed

The Sunday "show-n-go" 40 mile ride south to Belleair Beach then across the new Belleair Causeway was pretty uneventful until the last 3 miles. I noticed that my rear cassette shifting had become more difficult as we neared the last downhill (for Florida) piece of the ride. It seemed that the bike wouldn't hold whatever gear I tried to shift to. Then a big pop and all of a sudden the front cable connected to my Shimano rear cassette shifter disconnected from the shifter and was waving around like a loose piece of overcooked spaghetti. I have 8 gears in the back and 3 up front. So normally, I have 24 gears to choose from. Now the chain was stuck on the next to smallest gear in the back. My 24 speeds were down to 3 speeds. With the gears I had left I could choose to ride at 15, 21 or 35 miles per hour at a cadence of 70-80 RPM on the peddles. So much for my tune-up on Thursday. I'm not sure whether this cable has been replaced yet or not over the 17,500 miles that my bike has on it. Since it's Sunday I'll have to wait till Monday morning to take it in. I am glad, however, that this happened now and not on the RedSpoke ride where riding with only 3 gears would be much more difficult. In case you were wondering, my right shin is still swollen and red due to the mad bee or wasp that stung me yesterday. The Australian Bum cream has helped to control the itching but not the swelling.