We couldn't try the Impossible Burger because apparently there is a nationwide Impossible shortage. Instead we tried the Red Robin Veggie Patty, which is also vegan (just order it without cheese and in a leaf wrap). It was surprisingly good, even though we don't usually go for burgers with beans in them.
The wait staff and online allergens menu were very helpful. I got the broccoli instead of fries, but neither the manager nor I could work out why the fries weren't labeled as vegan, so I got an order of them too. They tasted amazing, and my stomach never got messed up, so we're assuming it's a "maybe they seasoning is made in the same factory as some dairy or eggs, lets be over cautious" kind of thing.
I'm so happy to find a new Gluten-Free + Vegan-safe place to eat! We're definitely coming back!