The tags are mainly just decorative, the important part is what is in the bar code. If the system does not recognise it as priority luggage based on the bar code, it will be sorted with the standard luggage. So even if the agent had attached a tag, the bagage system would not have sorted it as a priority bag.
Did you buy a fare that was an instant upgrade to F (don't know if AA still has those) meaning the underlying fare conditions where actually Y?