I mean, Ellesime's the queen of Suldanesselar. One of her subjects has demonstrated both the capacity and intention of destroying the realm purely for self-aggrandizement. Her punishment consisted in giving him another excellent reason to hold a grudge without in any way diminishing his capacity for revenge other than by putting a time limit on it. She then turns him loose in the world and, apparently, goes on as if nothing had happened. At least, there seem to have no arrangements either to keep track of Irenicus or to prepare defenses in case he decided to take the low road of vengeance. Unless the elves' world view requires them always to act with romantic and chivalrous folly toward one another, this isn't a woman vanquished by Fate but by Stupidity.
I think you are right here. Not to invest in some heavy-duty Joneleth-detecting spells does seem very stupid. Bordering on suicidal.
Of course, for all we know, elves very well might do just that -- to no avail. When a wizard of Irenicus' caliber wants to stay hidden, he stays hidden.