Sometimes pissed off sellers/foreclosures will do this to ruin the plumbing. I doubt this was an accident. Given the situation I would be very careful drilling the concrete.
You could make the situation worse if you drop a big chunk of concrete in your main line out to city. I would carefully try to get something very thin in to see how thick it is - like a metal coat hanger.
If it isn't "deep", I would jackhammer the area up and cut below the concrete line. And then replumb from there.
If it is deep you need to get at least to the first elbow and see if you have concrete there.
This isn't a terribly expensive thing if you DIY. It requires a jackhammer or sledgehammer, shovel, hacksaw, and corresponding replacement PVC. This isn't rocket science but you need to make sure you aren't dropping huge concrete chunks in you main line. I have been helping flip houses before and this was my biggest early mistake. I made a 4 hour job turn into a 20 hour job.