Are you freaking KIDDING me?!

We bought our house a year ago. Six months after we moved in, we noticed that the basement bathroom had a mysterious smell emanating from it. We've had plumbers coming and clean the sewer pipes, check to make sure everything is working,etc. We wrote it off as being from the big sewer pipe that runs through that bathroom and up and out into the backyard. Through all of this, we wondered where the basement drain was. We just figured the previous owners tiled over it. Well, in the last two months, we had a new surprise...drain flies. Finally, having enough of the smell and of the drain flies, J called a new plumber who we were referred to by Zoe's preschool teacher. He comes in and in a half hour, the mystery is solved. If you go in and look down the drain of our shower, you see cement. The missing drain, that we'd wondered about for a year, is actually back and to the right of the shower "drain". There is no connection. Wait...it gets better. Next to our shower down there, is a laundry sink, the pipe for the laundry sink goes back towards the drain, but again...it doesn't connect. So basically we've had water and sewage (because the drain is a SEWAGE drain) pooling up underneath the shower. Hence, the drain/sewer flies. So, in addition to getting our house ready for my father in law to arrive and getting things ready for Thanksgiving. John and I have to tear out the shower and clean (see BLEACH) under the shower and decide what to do next. What I want to know is how the previous plumbers missed this little gem and how the home inspector missed it. Now, if you'll excuse me...I have to go cry.