I understand exactly how you felt. I once had a FA chastise me on a WN flight right in front of other passengers for something I didn't do, and it was humilating. I immediately called WN customer service and filed a complaint against her.

Regardless of the airline, if any FA has an issue with a particular passenger, they should talk with the passenger privately. I agree with you that you need to discuss this with Alaska Customer Service. FA's need to take care of concerns while they are occurring, not afterwards.

I agree with the other folks that next time, buy a seat for your toddler, regardless of what airline you fly. It may make things easier for you in the future.