Can be brought on by a number of factors, including stress. Give the laminitis trust a call, they are brilliant and will tell you all you need to know. http://www.laminitis.org/
It is absolutely possible. Stress produces cortisol which is what is thought to trigger the laminitis. It is the same pathway as when cortico-steroids cause lami. My boy had stress induced laminitis last year when him and I had a nasty "little" tumble over a XC fence. Believe me that would have induced huge amounts of cortisol in his system.
Hope the horse gets better soon. Agree you shuld call the Laminitis trust. I found them very useful for rehabilitation advice etc.