The stems did have the white bristles that distinguish Hogweed from Cow Parsnip, but the determining factor was the seed shape. Here are the seeds of both:
See how the Hogweed seeds are oval and the Cow Parsnip seeds are heart-shaped? Here's our seed:
These are green instead of brown because they haven't dried yet. But they are definitely oval and not heart-shaped. Therefore, we have the bad stuff! Oh, no. I guess I need to call someone?