I had reservation pending to buy tonight (or miss the booking) and I want to get "Q" miles by "Codeshare".

AA metal DTW-ORD-BRU
DTA for Sabena BRU-TXL
and mirror return
Once an agent able to pull up AA6677 for the Sebena flight (but I cannot reserve that time) and now for my current booking, the agent said she cannot even "pull up" the codeshare flight number but only Sebena number.

Any method I can "suggest" the agent to locate it or I need a brand new reservation?

(I see this problem discussion in a past trend but no solution yet)