There is supposed to be a little 'stick on' pad on the back of the lever-like latch that holds the cover in place. Perhaps it fell off? If so, I'd just wrap the latch with a few turns of cloth electrical tape.... Only part about it I find really disappointing is the cover for the charging cord compartment. Complete junk. Already warped and won't stay shut...
And yes, the Volt is an awesome commuter car. We have 21k miles on ours. I've only added about 8 gallons of gas since new - mostly because of FMM.