That is most certainly a warranty and Cannondale should honor that, obviously they might need the shop to be involved usually with bikes you cannot file a warranty claim on your own but hopefully someone at the shop can help out with that even if closed and get you sorted. If not reach out to Cannondale directly and explain the situation. They may not have a bike to send you right now but see what is possible. I don't really fuss over a small scratch but cracks or what appear to be cracks are a different affair.

I can say if you had Synchro shift set up on the bike for Di2 that can cause front derailleur issues as it might shift at the wrong time. I busted my Ultegra front derailleur near the start of a 3 day ride going up a hill. My GM luckily had a Dura Ace front derailleur in his kit from doing NRS and one of the support crew picked it up for me but I opted to just ride in the small ring and spin out a bunch but have the easy gear uphills since I figured I would rather put it in a stand and make sure the firmware is all correct and see what may have caused it before just replacing the part and having it happen again. Needless to say for me the Semi Synchro just wasn't the move but Shimano replaced the derailleur under warranty and it is still going strong after 2 years.

I don't think I have ever cursed that much and so loudly for so long. I was pissed in that moment luckily I didn't decide to throw the bike or something stupid like that, that would have hurt. That bike is my baby (well one of many babies but probably the most prized)