I've seen rhubarb leaves get as long as my arm from elbow to tip of finger (and that was from a patch that was harvested regularly). The stalks don't have to be red -- there are some green varieties of rhubarb. But if the stalks aren't terribly thick or have branching of any sort, it's probably not rhubarb.

I'll forward the leaf picture to my sister and see if she can identify it -- she's got a Ph.D. in horticulture and works in extension.