The inventor listed on that patent is named Aric R. Voorting, but to invalidate it you'd need to prove not only that you came up with it, but that that person actually took it from you, which can be a challenge.
Back in the day, the USPTO worked off of a first-to-invent system. In essence, if you came up with it first, it was yours. Nowadays, however, it's first-to-file. That means that the first person to send in the paperwork is the one to get the patent (in laymen's terms, at least).
As George White has politely pointed out to me (oops!), this is old enough to be under those old rules, and first to invent is the relevant portion here. That means you'll want hard evidence, like timestamps emails or correspondences, etc.. Your best option is to speak with a patent professional--likely attorney--to discuss your options.
But in any event, you'll be facing a financial burden, and it'll be extremely difficult to prove. It's, as anything is, a business decision whether to actually push through and try to get it invalidated. Essentially, you'd likely be calling your own work prior art to the patent, but again, that's probably only worth it if you were intending to make money off of it and this has disrupted those plans.