The inverter is only rated for what, around 150W? No, it would take days to drain the battery from the 12V outlet. And the PHEV does not have a vacuum (even if it did, same story, it's a relatively low power device).
Yeah, but not in less than an hour. Just doesn't happen.
This is the only decent reply in this thread.
A lot of bad information in here. Considering this happened to OP in mild temperatures, let's assume even a slightly poor consumption figure of 500 Wh/mi. 9 miles would have used up 4.5 kWh. My PacHy typically pulls ~13 kWh into the battery pack, so OP would have about 8.5 kWh remaining for any climate use, idle use, etc. Under full load, the heater draws 7 kW... in 1 hour, that'd use 7 kWh. No (or very little) heat was used, and it was in the span of 42 minutes, not an hour. And, the heater does not run at full load the entire time. Once the cabin reaches a decent temperature, the draw decreases. And AC uses significantly less power - only 1-2 kWh once cooled down.
There is no good explanation for why your PacHy died after 42 minutes and 9 miles. Charge it up, and continue observing its behavior. If the range is not as advertised, take it back and do not stop fighting until they fix it. These can get 32 miles all day long in weather like that.