It sounds like she had a very bad fright. I wouldn't like to speculate, anything could have happened to her.
You might try getting her some Feliway (available at your vets and most pet shops in the US I believe).
I would also suggest the following: if she would tolerate it well, I would close her up in a quiet room (maybe a guest bedroom) with food, water, several cozy snoozy spots (one on the window, a box, a shady spot, some towels, etc), her toys and a litter tray (or two, if she perfers to use one for pee and a second for poo).
Make sure she is undisturbed by the kids. Go in and read to her outloud everyday, and spend plenty of time with her in here, pet her, groom her, anything gentle that she likes. If she sleeps with you, move her to your bedroom at night and close her in with you. If that's too hard for her, let her sleep in her den too. If you can, take a nap with her on the weekends, or if you are a SAHM, for an hour or so everyday. The point is to reduce her stress to zero while continuing to build up a bond with her while she's recovering from her trauma.
You may want to put a lock on the door to reduce tempation on well-meaning kids.
When she starts to seem more like her usual self around you and hubby, you can try playing with her a bit and see how she tolerates that. Gradually re-introduce her to other rooms in the house and the children one by one.
Needless to say, you probably have to have a chat with your children to explain why this happened and what you're going to do to help her and how they can help now (leave her alone til she's ready) and in the future (make sure she can't get out).