Well, it's hard to say for sure. If you raised it inside from an egg, it was probably not a wasp. I've had some caterpillars fail to shed their skin, or just die with no apparent cause. I wouldn't worry too much about the kids- My 5 yr old likes to hold the caterpillars and put them back on the leaves, and I don't think any of those have ever died, not even the ones that were dropped on the floor
If they're handled too roughly, they will spit up green juice to show their displeasure!
Also, I would avoid getting lysol or bleach or soap on the cats- cover them or move them when spraying would be my advice. I usually have mine inside on the dining room table, but with covers on their containers (plastic tubs).
Also the 5ths will usually stay on a leaf in a tub, but if you put them on a stalk they may wander around to find a leaf that tastes good. If you end up with two on a leaf, don't hesitate to pick one up and move him (or her).