Here’s another usage note under the definition of “snuck” from the Houghton Mifflin Dictionary:
Usage Note: Snuck is an Americanism first introduced in the 19th century as a nonstandard regional variant of sneaked. Widespread use of snuck has become more common with every generation. It is now used by educated speakers in all regions. Formal written English is more conservative than other varieties, of course, and here snuck still meets with much resistance. Many writers and editors have a lingering unease about the form, particularly if they recall its nonstandard origins. And 67 percent of the Usage Panel disapproved of snuck in our 1988 survey. Nevertheless, an examination of recent sources shows that snuck is sneaking up on sneaked. Snuck was almost 20 percent more common in newspaper articles published in 1995 than it was in 1985. Snuck also appears in the work of many respected columnists and authors: “He ran up huge hotel bills and then snuck out without paying” George Stade. “He had snuck away from camp with a cabinmate” Anne Tyler. “I ducked down behind the paperbacks and snuck out” Garrison Keillor.