Unable to collect seeds, we searched for the plant online, thought we id'ed it, and ordered seeds. Neighbor friend planted them at the base of her picket fence and waited for them to fill their allotted to 2'x3' space. At two feet, they were still growing. At five feet, they were still growing. Within a couple of months they could have been used as Christmas trees in someone's soaring entry hall as their hulking pyramid shapes topped out well over 8' tall with an equal spread at the base. Methinks our plant id'ing skills failed us!
We still don't know what we first saw but we do know that what she grew was hibiscus radiatus and when I inherit a 20-acre garden from some benevolent stranger I may plant it again. In the meantime, it is preserved in pictures and in memories of its beautifully colored flowers and viciously prickly seedpods.