Apparently, my opponent, NosyRat, had a unit of his skirmishers pursued by my elephants. My elephants promptly hit a unit of thureophoroi and engaged. For some reason, NosyRat found an 'undo' button available on the skirmishers. This prompted the elephants to swap places with the skirmishers, remain in melee with the thureophoroi, who were now a fair few tiles away and facing the wrong direction, and then break off when I tried to trigger melee the next turn.
Ladies and gentlemen, I present to you the first ever case of teleporting elephants. (Apologies if this is not the first case.)
I've attached screenshots to show what happened.



