You should carefully think about the steps you preformed to check each sparkplug and then reverse them, to see if you missed anything.
In most cases, if you forget to plug in a spark plug wire or add a spark-plug, the engine will still turn over and potentially run, although this can cause engine damage. However, if the engine turns over(makes noise) when you use the start key, this could be related to sparkplugs.
Assuming you ONLY touched the spark plugs, it would be a good idea to make sure all the spark plug wires are connected and the spark plugs are all firmly, but not too tightly screwed in.
It is certainly possible the battery is dead too, you would be able to check by turning on the switch to see if you get radio ect.