My brother did some investigating in the paddock & maybe our girl might have been eating some loose dirt/soil. She's a bit of a chewer & digger and a great one for ripping up clumps of grass roots and all and then eating it so that would fit the profile.
I never gave it much thought up until now but given her habits then it might have been like a Sand Colic type thing like I believe they can get in SA & WA? I think I'll go and check the manure piles tomorrow and see what's there. When I saw her again this afternoon she was back to her old irrascible self & she had some paraffin on her backside and hocks so clearly it has been and gone too....and everywhere I expect.
Years and years ago the late Charlie Parsons told me NEVER under any circumstances to let a horse with suspected Colic get down on the ground.
He reckoned if they rolled over on their backs or got down and thrashed about that their insides were sure to get twisted & then they'd be gone for all money. He also said if they had gotten down then drag them back to their feet and then make them walk. Of course that all depended on a person being fortunate enough to be right there right when it was all happening.