RPGMemes

100% this. The most important thing in my opinion is to to make a good-faith effort to get an accurate ruling (steps 1 & 2) but barring that just make a quick ruling that won't slow the game down and move on with the fight. Keeping the game moving along is an important role of the DM, and no player enjoys sitting there while two other people debate the minutiae of a potential ruling. It's happened to me a few times where I've started a session with the players saying "Last session X happened, but it turns out Y should have happened. X will still stand as happenex, but in the future it will be handled as Y."