He sure is feeling his oats...uhh....Strategy
It used to be very dangerous when a horse got in the feedroom....at the times straight grains were fed. Oats, for example has 44% sugars, corn close to 70%, the Strategy has 23% or so. So you can imagine that a thief did get a bad case of laminitis after chowing down on grain all night.
It is still a risk, if you have an overweight horse fed a high sugar diet.
Still, keep watching, just to be on the safe side.