I have no idea whether non-custodial parents are primarily to blame -- these stats cited by ABC News just say family members or parents.
"203,900 kids were abducted in 1999 by family members or parents. Approximately, 58,200 were 'non-family' abductions — only 115 were defined as the frightening kidnappings by strangers." -- http://abcnews.go.com/US/story?id=91365&page=1
Unless almost all of the family cases are non-custodial parents, your claim of hundreds of thousands seems a bit exaggerated. Some of these must be custodial parents, uncles, grandparents, siblings, and so on.
I think 'non-family' means acquaintances, minus the 115 cases of abduction by a stranger.
One non-profit that works in this space estimates that 78% of the "family member or parent" abductions are due to a non-custodial parent. That would put the total around 159k, which puts the parent poster in the right order of magnitude.
BTW, in addition to wikipedia's contribution to society of a free encyclopedia, I think this phrase is a great contribution. As Gerry Sussman says, "once you can name a spirit, you have power over it."
Citation not needed, because this is a conversation, not an encyclopedia article, and he gave a rough order of magnitude estimate which happens to be reasonably correct.
