That may be true, but I’m not aware of any other games that lose their game state when this happens. Does something similar happen to Siralim on iOS when the app loses focus?
Bard’s Tale on Android comes close to having a similar issue. If you exit the game without saving first you get a dialog telling you that there is unsaved progress and it asks if you want to recover it. As near as I can tell, Bard’s Tale essentially journals game state while running and can reload it when you launch the app again.
“Unfortunately, this means that there is nothing we can do about this on our end.”
Nonsense. Adding a layer to journal game state when the app loses focus and reload it again is perfectly possible. The Return on Investment may be too low to be worth the work, but that’s different than being impossible.
“When you exit the game, the dungeon you were in is not saved”
That’s not accurate, at least not on Android. When I go back into the dungeon through the castle portal the explored areas are visible. The emptied chests are still empty and the defeated monsters still quite dead. The dungeon is still there. Its state has been preserved. The only thing that HASN’T been preserved is the location of my party within that dungeon. We’ve been moved back to the castle.
Since the dungeon persists, how about you modify the game save system just a tad so the secondary objectives are stored and reloaded with the rest of the saved dungeon, and you can go back into a dungeon you’ve already visited without paying the portal use penalty a second time? I’d still be reverting back to the castle, but if the secondary goals don’t get reset and I don’t have to pay the portal use penalty again, it becomes a quirk instead of something that interferes with my enjoyment of the game.
“Each dungeon takes about 10-15 minutes to clear completely, so this shouldn’t be much of an issue.”
Protip from someone with a bit more software customer support experience than you: Telling the customer that their negative experience with the product isn’t that big a deal only annoys them. It doesn’t help. Honestly explaining why the problem is too expensive to fix, that tends to work a bit better.