Sorry but you can't get a refund because of a medical emergency. No site, whether Ticketmaster or a third party site, would do that.
Hi @florerot
I hope your husband is doing better as that is the most important. Did you buy insurance for the event? If you did not then it is unlikely that you will get a refund. The seller sent you tickets. Stubhub facilitated the sale. IF you could not go you could have always put the tickets back up for sale on Stubhub.