Acute laminitis generally shows up about 72 hours after the initial cause. Lots of walking exercise in the interim is the best thing to do to ward off the worst of the pain, as walking will help the horse metabolize what's going to cause the problem. If you are pretty sure he's in for a bad bout, have him trimmed BEFORE the pain sets in, as ANY excess wall will work against him when the inflammation hits.
Signs include noticeable heat in the hooves, BOUNDING pulse, and stance where the horse puts all his weight on his hind legs and is reluctant to walk or walks as if on eggshells.
Cold therapy can help minimize damage, don't make him move during this time (the acute pain stage lasts about 72 more hours). Let him lay down if he wants, and only give him hay to eat. Some people like to give Bute or something for pain, but in this case, the pain keeps him from doing more damage to his hooves, so letting him ride it out may actually prevent more suffering in the long haul, but that's for you to decide. If he has shoes, pull them now! Keep him quiet until the acute phase has passed. Once he's comfortable in a couple of days, start handwalking him and letting him exercise in a dry lot. Don't make sharp turns (that tears up the damaged lamina). May need a trim in a couple more weeks. Build up to more exercise and keep him on short trim schedule (every 2-4 weeks instead of the usual 6-8 )
If in a few days he shows no lameness or heat, he probably made it through alright, but I'd sure be upset that they just tossed my horse out like that, when they should KNOW BETTER!!