OK well I can't know for sure, but it's VERY possible it was the ice cube. Mine have puked immediately after drinking very cold water, swallowing ice (they are fine if they chew it up first) and also when they eat something very hot (usually a hot piece of boiled potato... we do our best to keep them out of the kitchen but
)
The antibiotics could also make his stomach upset.
If he just threw up the one time, I would just watch him and see how he is acting. It's probably fine. If it persists and you think he might be dehydrated or ate something dangerous then I would take him in.