My sister handed me down a Gucci horsebit leather bag a few months ago. It is missing a screw at the top of the bag and the inside zipper is broken so I went to a store and they sent it out for repair. The reps at the Gucci store even fell in love with my bag. After two months, I call Gucci after not hearing back and I was just told that the repair team determined that my bag is "non-gucci." I'm 1000% sure that this bag was bought from Gucci. My sister gave it to herself as a gift when she graduated Harvard law school and it was A LOT of money! She doesn't have the receipt because the bag is super old now but it's in mint condition (except for the missing screw and broken zipper). What should I do? I was in shock when I heard this? Has anyone experienced this? I am sooo upset that I want to cry. 
This is the bag:

This is the bag:
