Did they not let you know before leaving Dallas that you would miss your connection?

Did you ask the gate agent why he didn't have a hotel voucher if he had just issued one to the F/A?

Did you ask someone else for the voucher?

If this wasn't a weather-induced situation, I would get a hotel and submit it to Southwest or your credit card trip delay benefit provider for reimbursement.

This sound like a missed connection. You arrived the next morning. It's unfortunate and inconvenient, but I'm not sure that qualifies as a "horrible Southwest experience". If you submit your story to Southwest for additional compensation, I would keep your narrative factual.