I was installing some mods for World of Warships via Aslain’s mod installer using the “Run EXE inside wine prefix” menu option. After it finished I went to Kill all wine processes. As I clicked, the World of Warships list in Lutris disappeared. The game still exists on my hard drive, everything is still there, just Lutris no longer lists it.
I see that someone else had a similar problem but it has gone unanswered.