I tried to report the user in game, but could only do so for spamming, and the help menu only allowed me to report buggy interactions.
One of the options in the Help Menu is "Report Player". It is a very open ended report, allowing you to state whatever it is you wish. That said, I still strongly recommend simply emailing us.
On top of that, the game specifically said that it was waiting for the player to end their turn even after 15 minutes
This is what leads me to believe the entire scenario was a de-sync. Once a de-sync occurs, a large number of things can go wrong in exceptionally strange ways. They don't happen in large magnitude very often, but due to the way communication works, it is a possibility. I try to never rule either side out, as both are *always* possibilities.
An Endless Turn is a symptom of a De-Sync, and when an Endless Turn occurs, you'll see that message sitting there forever. Anything could have *created* the de-sync, and without the output log/game log we can't know what it was.
That is why I felt it necessary to report it here as the confluence of anomalies greatly favored my opponent.
It generally will regardless of how the de-sync occurred. You are seeing one thing happen, while your opponent sees something else, or isn't even in the game altogether.
I realize that my knowledge is lacking, but how did I display that here?
Simply the amount of assumptions you made, which then led to you proceeding to "Call your opponent out". Without full information, the actions you'll take accordingly can be mislead greatly.
For context, I wasn't specifically saying you shouldn't have called your opponent out with The Calamity, I'm saying you shouldn't have called him out period. If it's a de-sync and your opponent isn't actually doing anything wrong, you're speaking in an incredibly brash manner towards them and antagonizing them wrongfully, and you would in fact be the one in the wrong.
This is why I say simply make your reports straight to us and we'll talk to you about it. Bringing it up to your opponent can lead to a large number of bad situations, depending on what's actually happening, and no one wants that.