Hi Mark, here's how I see it...Spink is definitely within their legal purview to refuse to refund you even a penny because of their stated auction guidelines (and the fact that you are way outside the time frames they have in writing). They could and likely would argue that because you bid that this necessarily means you agreed (implicitly or not) to their terms.
I'm not at all saying that you shouldn't communicate with them to let them know what happened, it's just that, as you already suspect, they will likely not refund you.
Also, I don't know if Spink or any auction house accepts PCGS/ANACS/NGC's judgement as the definitive word on whether or not a coin/medal is in fact genuine. I don't even think these TPG's can guarantee that their evaluation is definitive proof....although I'd suspect that NGC's graders are highly qualified in determining the authenticity of that type of medal since they have graded several and they generally are very thorough in their evaluations.
A final thought......I know that some people don't like buying on eBay.....but if nothing else, what eBay has going for it that is unmatched by any auction house is it's Buyer protection. I've had more than one time where I purchased coins on eBay and after sending them in for grading, received a couple back about 2 months later that were genuine but were not in a condition that was described in the auction. And yet, I was able to get a refund for the full sale price and shipping costs. I was not able to recover grading costs but at least I got a full refund on purchase price.....long after the transactions ended.
Mark, you have taken this all in stride and I do appreciate very much that you've shared this experience with this community....it is a good lesson to be learned for all of us.