^ Ditto. I'd be more apologetic about my loose horse eating someone else's grain (cuz we all know that ain't cheap!!), and offering to replace it then to be mad that you let the horse out to get some movement in its system.

That being said, I have a 1200 lb Perch/Paint gelding who - when we first brought him home to our farm - was (and still is) a Houdini (but a controlled one now that we found the right latches), and one time he got out and ate nearly half a bag of sweet feed, a bale of hay, and he was absolutely fine. No issues...

Hopefully the mare is all right and the owner chills out too!