Yes, any plant could make a mistake and all of them probably did at one tiime or another. Mistakes involving serial numbers were more likely to be made in countries where the primary language was something other than English, but I've seen scrambled serial number prefixes from one or two "US" plants too. Plants also could make mistakes with style numbers. And a few plants operating right before and during Coach's switch to Chinese production had all sorts of odd mistakes because they had to use whatever creed and serial number stamps were left over and hadn't been destroyed or sent to China.
That's why we really discourage anyone who doesn't have a text and photo library of real, fake and questionable bags and stampings to not try and figure it out on their own.
Also, sorry to bother you with another question but should all Coach items, big or small, have the serial number somewhere no matter what year they were made?
No. I suggest you read the Salearea Coach Guides or at least the ones on Creeds and on Serial numbers. Throw in the ones on YKK zippers and Authenticity Guides. Heck, as long as you're already started, read all of them.
https://forum.purseblog.com/threads/salearea-guides.983575/#post-32252957
I know they permanently moved the serial number from the creed to a small white tag at around 2014 but it looks like they are back to stamping them on the creed. Are they stamping the serial numbers on all creeds now? I know small items do not have the creed anyways so they would still have the white tag. But do all small items from even before 2014 have the white tag?
I don't think ANYTHING from before 2014 or when they temporarily stopped using stamped numbers on the creed had a white tag, including small bags without serial numbers. But I'm definitely not an expert on newer styles so if you have questions about a specific bag, please post in the Authenticate This Coach thread. There are NO solid or fixed Rules, Coach changed them often. That's just one of the many reasons why almost every so-called Authenticity Guide on the internet is useless, most of them are years, sometimes almost 2 decades, out of date.
I'm wondering if this holds true for like giveaway bags and such.
I'm not sure what you mean by giveaway bags. We've seen bags made in limited numbers for special occasions or groups (Stuart Vevers' 10th Anniversary, a few NYC dance companies, etc) where some have "normal" serial numbers and some don't. Coach makes up their own rules about that kind of thing.