My household just got the burglar event trigger (not by cheats and not using the lot challenge), and to my surprise, the sim that showed up is some randomly generated NPC, not Robin Banks (who I was ...
Ideas
Hi ! As you all explained, your save files were created pre-patch: as it's not possible to add new NPCs to an existing save with an update (as it was for the new houses in Willow Creek or Oasis Springs, as all of that is tied to the files used to generate a new save), the games generates a random NPC to fill-in the role of the burglar.
One easy solution to fix an existing save would be to grab Robin Banks from the gallery (look for "Banks" in "Popular Now" and you might find some people uploaded her) and place her in your game. As NPCs careers (like the one used for burglars) are deleted when a Sims having one of them is played, do not install her on a lot and don't play her.
So to do it, go in Create a Sim, find Robin Banks on the gallery and select her household, then Validate and when you are in the Manage Worlds screen asking where you would like to move her in, just Cancel Moving. If you already had a burglar generated, find them in your Unplayed Households and delete them - if you don't, either this burglar and Robin Banks would be used randomly.