Interesting....did you loose the bolts? You will need to go to a Kia dealership - parts dept, pull up the schematic diagram of the engine cover, get part numbers and order some new bolts. Should not be very expensive.
Long story short. I removed the cover when i lived on the east coast to change the oil. Didn't think it was relevant and left it when i moved to Washington State. Rains alot here and. Water gets in the manifold making it surge and stall. Replaced the maf and intake hose. Now need to get bolts for the cover to keep condensation off engine.