I had this happened where it was successfully drained. The good part was that it was over the bathtub, however the bad part was the pregnant belly being all tile. That would hurt. Anyway, I took the smallest drill I could find and created holes through the grout in a few places. It eventually drained enough to not collapse, and the contractor could take it out in a controlled fashion.

In this case the person suggesting tape seems like a really important idea so you can make a drain hole without it ripping open and bringing it all down at once. Grab some towels and buckets, and spend a few hours getting that water out before it makes things worse