It looks like it could be a single flower bud coming out of the spur on the peduncle, but I suppose that depends on the species. It's possible it is a seed pod, but it looks like it might be the part that holds the pod. I found the below image online, which looks almost like it might be an advanced form of what you have!

Some Hoya species can self-pollinate but as far as I've heard, Hoya can only be pollinated by some sort of flying insect, usually moths. Some people put their blooming Hoya outside at night in the summer near a light so moths will come and pollinate, but as you said, it was never outside while blooming. Could a marauder moth or some other flying friend have come in and pollinated your Hoya without your knowledge? Nurseries also tend to have plenty of bugs around so... anything could have happened.

Were any other Hoya blooming around this one at the time? Hoya can totally cross pollinate depending on the species. Hoya "mathilde" is a cross between Hoya serpens and Hoya carnosa. Lot's of Hoya hybrids out there! You might have one too!

Wow. I have no idea! But please keep us posted!

Thank you for responding! Since I posted I have browsed images of Hoya seed pods and believe that’s what it is. It is Hoya australis ssp. Australis and they only bloom once a year in the fall so it’s not a new flower bud. So this has me confused. With some Hoya growers keeping hundreds of different Hoya species in close proximity of each other, why isn’t cross breeding a common occurrence? There should be tons of mystery hoyas out there, no? The vendor I bought it from said it was the only Hoya he had, and the only Hoya I had blooming at the same time was Hoya sunrise. I will definitely post more info if it matures. Sara