I tried the record locator. That didn't work. When I was able check in, I saw the AS record locator was different than the AA record locator.

In any event, halfway down the e-ticket confirmation email received when booking on AA.com is the section with the fare info and ticket number which in my case was 001XXXXXXXX11 (the x's were all numbers). I used that number and was able to check in on AS.

My upgrade didn't clear and hopefully AA will see me as having checked in last night so I am higher priority on the wait list.

The odd thing is that I was able to get my AA boarding pass. Interesting that AA can't give me a boarding pass on a codeshare operated by AS, while AS can give me a boarding pass for an AA flight. I'll still check it at the AC but its good enough to get me through the airside bus connection at LAX.