Possibly? It says he was 4ft something, so I took that to mean he was a very young child at that point.... It may be that his parents, not knowing what was wrong or having the resources to find out (like parents do today) they may have turned him out. Or maybe they would have thought he was possessed because of the rocking etc? Anways, after they turned him out, he wasn't able to fend for himself on the streets because he lacked language, or wasn't able to communicate properly with people, or other homeless children (didn't know body language, or spoken nuances etc etc) and people would have treated him badly because 1)he was on the streets (think street urchin) and 2)because he was an "idiot". Being unable to steal something because he would have been clumsy and not able to be subtle about things, and unable to get a job for whatever reason, and people would have been mean to him or said harsh words, he turned to the woods in order to get sustenance etc.
As for him not learning to speak: Because people were mean to him and because he would have been very young when he went into the woods, he wouldn't have a good grasp on language to begin with and may have developed an aversion to it? But that seems a little far-fetched, so:
I think its easier to learn to speak when you're very young, and that is the theory behind teaching your children to speak several languages at a young age, that some parents are trying nowadays... There was a story on the news one time where this girl was abused/neglected. Her mother was mentally ret*d or something similar, and abused the girl. The girl first learned to speak by listening to the rats and squeaking like one. She was 12 or a little older when someone finally got her out of the home, and she never learned to speak.
(It was on the American Broadcasting Channel [ABC], like Dateline with jon straussel-sp- or something)
That would be my theory, anyway.