According to Kathy Love's "Corn Snake Manual"........'the first Striped Corns were hatched by Mike Nolan in England in the mid 1980s. Ernie Wagner imported the original parental stock and some of the striped babies into the U.S.'
From Kathy's wording I gather the first Stripes were hatched from normal looking adults. I'm not 100% sure so your best bet is to email Kathy directly on that.
kathy@cornutopia.com
On a sidenote, in the Corn Snake manual there IS a photo (page 98) of a Striped Corn hatched from eggs laid by a wild-caught specimen at a dealer's shop in Tampa, Florida in 1980. (It doesn't say in the book what happened to this animal. Whether it was bred and is responsible for another line of Stripes is anyone's guess. Email Kathy, she probably knows either way.
)
The animal pictured on page 98 looks EXACTLY like every normal Stripe I've hatched, so I'm quite sure the Stripe morph in corns is NOT the result of hybridization with other ratsnake species in Florida. 
Attached is an older image of a Stripe het anery/amel/hypo I hatched and kept back in 2003. 
BB

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"Have you hugged your drummer today?" --- Me