Ah as someone that works in IT I've seen this more than once. The best course of action is to be honest to your IT dept. Trust me they'll know. I only say that because they can take it apart and try to clean/dry it as well as possible. If you drink your coffee black you may be lucky, the more sugar and cream you use the worse the damage. It also depends on how much liquid got in and depending on the model what components were affected.
Mistakes happen, I've never seen anyone fired for spilling, dropping or otherwise unintentionally damage their computer.
Good luck
