I would like to confirm the following -
1) being on a AONE/DONE fare, you were booked into fare class A.
2) You were a OWE at the time of travel.
3) the flight you were travelling on was the one you originally booked (not on a standby or interrupted op flight).
4) You were at the gate at the start of boarding (not near the last to board).
If all of the above were true, I find it very hard to believe you were the lowest ranking F passenger and therefore the one to get bumped. There must have been someone on a KUPP/YUPP fare in fare class P or on an award booking in fare class P. You should out rank these passengers automatically. I would also like to think that being OWE, you would outrank most others in fare class A. Only fare class F would be clearly above you.
I have to say I would complained quite forcefully if this had happened to me based on the above. However, personally, I may have considered the USD500 voucher as I travel on AA regularly and therefore it may be quite useful as AA F is pretty poor on that route. I would also have a word to QF (for their information only) about how AA is treating QF WP.