Not to mention that there was a Next Level Urgent Care right there - the Elder Brother of the monks is renowned healer and people came from all over so he could take care of them. That is said explicitly in that Brienne chapter where she sees the gravedigger.
So in the books at least, not only is it cleanly set up for Sandor to be alive (and hinted at very strongly) but there's also a setup for why someone else might come to the island looking for a healer and realize he's still alive. (For example, Sansa, who is almost next door at the Gates of the Moon and in charge of Sweetrobin who is sickly. Not that I expect that to happen, but there's a setup there for something like that).
But the show has changed so much about what's going on in that area that I have no idea how they might bring Sandor back, if they do. Brienne doesn't go to the Quiet Isle, Sansa isn't at the Gates of the Moon and Jaime's not roaming the Riverlands. For all I know they'll make Sandor a Faceless Man.
So in the books at least, not only is it cleanly set up for Sandor to be alive (and hinted at very strongly) but there's also a setup for why someone else might come to the island looking for a healer and realize he's still alive. (For example, Sansa, who is almost next door at the Gates of the Moon and in charge of Sweetrobin who is sickly. Not that I expect that to happen, but there's a setup there for something like that).
But the show has changed so much about what's going on in that area that I have no idea how they might bring Sandor back, if they do. Brienne doesn't go to the Quiet Isle, Sansa isn't at the Gates of the Moon and Jaime's not roaming the Riverlands. For all I know they'll make Sandor a Faceless Man.