I found these. https://www.campingworld.com/rv-sewe...gs-104644.html
Thanks for reminding me. The fiasco I described happened on our last trip out.
It was a bit out of angst. We no longer store at an RV place that has a dump, as I now have an enclosed building to store in, but I can't dump there, and I can't dump at home. If we don't dump at our last stop, our only option is to go to the city sanitation dump where all of the honey wagons empty.
I think I may have also been distracted by the size of the dump pipe, as at this place it's about an 8" port. I was thinking I better not let go of the dump hose as I didn't want it dangling in there, and certainly didn't want to drop it into this huge tank I assume is under there. That's probably what distracted me, and I forgot about the caps.
As embarrassed as I was at the time, I can look back at it and laugh because no one got hurt, and nothing got damaged. Worse things can happen.