If it's the plastic trim piece from under the bumper (usually they sorta look like "ground effect" bodywork on stock cars--think NASCAR), they are held in place by a line of plastic push connectors. Likely, when you hydroplaned, the water hit the trim piece and pulled the plastic clips out. (It's also possible that the plastic holes where the clips attach ripped through). It's an easy fix. 1. If the clips are gone but the holes are ok, go to an autoparts store and buy the push in clips/connectors. The come in little packs of 2, 5, 10 etc.2. If the holes are ripped out, repair the holes with JBWeld (The KwikWeld version will be fine) and once it's hardened, reattach with new clips.3. Just pull it off and go for the "In your face!" barebones look. People pull that trim off all the time on curbs, parking stones and snowbanks.
I'm pretty sure that anything that will be stopped by the flimsy piece of plastic wont hurt the oil pan, besides that's not what it's there for. Its partly for aerodynamics and adds like 0.05% fuel milage at highway speeds, and helps keep water, mud, what have you from getting the engine wet. It's really not a big deal, theres still a lot of cars that dont even come with them, and older cars never did. You can safely ditch it, or just ghetto rig it back into place if you want to keep it, its not worth spending any real money to fix it.