What I see here is that the OP requested a baggage fee refund from UA, instead of US. Therein lies the problem.
UA had nothing to do with the baggage fees of US, and could only assume that the OP meant something else.
Sounds to me that the OP screwed himself by trying to save a measly $25.
That someone at UA figured out the problem and offered the OP 30,000 miles, is a miracle, IMHO.
The OP made the mistake, likely due to confused information from whoever told him about getting a baggage refund at US.
Take the miles and consider it a lesson learned.