Thanks for all the help and guidance guys.

I found out more info and now this complicates things. They were booked on LH, they checked in bags with LH (AMS-FRA-YVR) but it got cancelled. They were told that the bags will be transferred to their AC flight(is this even possible)??? but they clearly did not make it or something wrong happened there.

They called LH and LH hung up on them twice lol and told to call AC. I told them to give AC their original LH flight numbers. I personally think the bags are still in AMS and LH didn't transfer them properly or even if they had to capabilities to transfer them. I figured if the flight was cancelled, they'd have to pick up their bags from the cancelled flight and re check with AC. But LH told them it will be transferred. I don't check bags so I dont know what the process is for checked bags on flight cancellations w/ transfer to a new airline.

Anyone have further thoughts based on this extra info?

they called baggage line, made all the claims etc but AC cant even find the bags or where they are at all. Makes me believe that it is still in AMS and LH messed up telling them the wrong info.

Thank you again so much... sucks for them as they don't really care about compensation but just really want their stuff back.