FYI, I'm sure you didn't hurt anything, but there is no need to cover (or with a rock). The purpose is not to drown or kill the insect. There is no call for that, and covering wouldn't kill it anyway. You are just proving (with the water) that this is not a good place to set up house, and encouraging it to go somewhere else. Since it is a new nest, there is nothing that will encourage it to come back.
When you spray during the day, you will usually see the wasp exit if he is in there. They usually just sit around for a while to gather their wits or dry off (or something) before they leave. He won't be mad.
