2004 Chevy Aveo Oil Leak Permanent Damage?

Got an oil change yesterday, drove it fine for two trips (totalling about 30 miles) until I start to hear a rattling sound from the hood, which corresponds only to when I give it gas. It sounded like paper "flapping" in the wind or something. At the time, no warning lights showed up.

I pull into a parking lot, sure enough oil is leaking under the hood, the oil pan cap is missing, and the dipstick is almost bone dry.

Fortunately, my car seems to run fine now (towed it back to the service station), but should I be worried that long term damage was done? Would it be worth my while to have it checked out for a second opinion? Many thanks.