The point is that if you google "sneak peek" you get 1.410.000 hits and you get 1.320.000 for "sneak peak" which is way too much for a misspelt expression, especially if you think that you can find it also on reliable websites..I think it's just a mistake on the part of the writer. A sneak peak... what would that be... a crafty mountaintop? No, you were right from the start, Paulfromitaly. It's "sneak peek".
You're right, although for example this site has nothing to do with the electronic world and I'd expect a big recruitment company not to misspell words...Googling "sneak peak" (UK only) gave 8 out of the first 10 as something to do the electronic world, mainly gaming, and one blog. This left one which may be a play on words but I think was a simple mistake.
I think the million plus hits indicate it may be part of a gaming dialect or even dialects. Gamers access and use the web a lot.
The website is "under construction" says the link. It's a spelling mistake by a web designer. I would bet a pound the designer spends some of his (or possibly her) leisure time in this parallel world. The spelling seems to have become normal there.