This topic was already discussed at length previously. I'm not a US employee, but as I understand it, it is part of the US Airways f/a contract that if you do not respond to a recall letter, you are assumed to have refused recall and are removed from the recall list. At least, the US f/as have the ability to "pass" on the recall. But, you have to let the company know that you are passing. No response does not equal pass, it equals refusal. We don't have that at AA. If recalled, you have to come back or be removed from the list.
Some furloughed f/as seemed to be upset because the recall letter did not state this even though it is not the company's responsibility to see that the f/a understands their own contract. Others seemed to think it was the union's responsibility to remind them that they had to respond to the letter.
If I misunderstood the previous discussion, I'm sure someone will correct me.