Is it a broad bean?

Yes, it is a broad bean or maybe a tick bean, though now it will be a has bean! This is not a current photograph in the UK, look at the surrounding vegetation!

What makes you say that Bulbaholic? I assumed it was last year?

I like that about a has been ,but you are wrong it could have been taken in emerdail they have had no snow or ice,

It looks so healthy, perhaps we should all grow our beans by the roadside, maybe it likes petrol fumers

You should have returned later to harvest the crop!

lol
It looks really healthy!

Do you think an animal buried the bean because it is very dense to self seed?

Field beans which are a type of broad bean are grown as crops in lots of places, and also used as a green manure. I'd guess this is just one seed that got left behind or dropped after harvest.
I just wished mine looked that healthy! I have terrible trouble in growing them here as they rot if planted before winter, and in spring seem to develop some kind of fungal disease that turns all the foliage black.