Guessing that they don't really need to show at Pitti Uomo anymore, as buyers will still be making visits to the showrooms in NYC or Tokyo anyhow. Could be something else going on too, as other big names are starting to opt out of Pitti as well, including Nigel Cabourn (who will be showing in Paris this year instead).
No online store, just a blog: http://jackstrawclothing.blogspot.com
They take phone orders for sure, not sure how good they are with email though. Jack Straw is the only store in town I like these days, so I support them where I can by spreading the word on sales and such (and for EG fans, they've become a great resource).
Jack's Straw sale started today, lots of good stuff left from EG, Barena, and Boglioli. If you go in also check the sale bin for past season stuff with crazy markdowns - I found some old CdG jackets for cheap.