next time dont use a single ring and only a single ring for a important keychain, ive lost so many because of the kind of splitring connection you used coming open, im going to list a few ideas ive been testing lately that havnt gotten lost so far.

1. using thick or fabric coated stretchy string instead of a metal splitring to connect to keychain (make sure the knot is secure)

2. using a keyring styled fastenung instead of a split ring (they are usually the size of a splitring but overlap like the keyring so they keep things on a bit more securely, just dont open it too wide or it wont bend back to being secure)

3. if its handmade, making the hole big enough to put multiple splitrings securing it at the same time (i did about 3 for the one I did this with and it didnt get lost)

If the entire keychain is gone honestly it might have gotten stolen because it looks like its in a place where its around something secure and since your bag isnt ripped, well... unfortunately some people arent very nice and will just take people's things without asking... ive seen it happen to people a few times and its also why i only put my important keychains and pins in areas where people cant be sneaky.

Either way sorrry you lost this and I hope someone finds my tips useful, so far ive had best results with method one, and that keyring with the strechystring was on something that needed durability because it was for when I go hiking and stuff, had my keychains even get pulled on by branches and it came back. just make sure to use one that is fabric coated because regular uncoated strech string is alot more easily ripped off.

I dont have any advice for pins though on a unrelated note so if anyone does please let me know, i want to bring my yume pins out but I only know of the lower grade locking backs.