As it turns out, the builder’s installation plumbers chinsed out and NONE of our toilet and faucet attachments were up to code. This was just a matter of time. Good thing this was in the basement (and I had fallen asleep down there).
The clean up crew removed a shitload of water, and we moved everything to the garage and loft. All the wood furniture is fit for throwing out. The bottom two feet of the drywall was removed, and everything is drying out.
Addendum from May: I get my car back tomorrow. Unfortunately, my garage parking spot has been taken by wet basement furniture.