Squishypuff wrote:
I know Buddy enough to know when his lying down is abnormal...

That's the most important thing, knowing your horse.

The vet has seen him in the last month, and there was nothing wrong with him- what is the something more you think could be wrong?

The colic could possibly stem from something else. It could also, just as easily, be a one-time occurrence.

Just think about it, when you're not stressed, Squishy - was there anything different in the last few days? More hay, less hay, different feed, did he run out of water, was it especially hot.... there are a lot of things that could cause a mild, one-time colic. You may well be able to pinpoint what caused it.