sounds to me like the poor wheel build weakened the wheel and allowed the ding to happen.
Not true (no pun intended…). A little dent to the rim, as described by the OP, could happen on any quality of wheel build. As he's said, the little dent isn't really an issue.
The issue is that the wheel simply should not have loose spokes, after any amount of time, unless it actually gets properly flat-spotted (written-off rim). matthew_h is on the money: re-truing after a few weeks is a myth. The spoke tension should be checked and perfect at the time of building, if the wheel builder is any good (and, not to blow my own goat, but I'm a pretty fair wheel builder).
Sounds like the wheel build was a little shonky in the first place. I'd get them to re-build it, and not use cheapo plain-gauge spokes. There's no reason to ever use plain-gauge, other than cost.