Should one ever experience a zipper pull breaking or falling out, this is actually fairly normal! Ask the Airlines LOL!!! Due to the continual nature of pulling and torquing our zippers, the body clasp can actually widen a bit allowing the pull to fall out.  Some more complex and custom zipper pulls have plastic or other sheaths that can break off the pull-base itself.

I post this for those that belong to BOOQDOM, owning a booq product.  Should you ever loose or break a pull, let use know.  The fanatics at booq will send you some pulls in zippy-like fashion; let us know and we'll help the matter zip along!

Here's booq's instructions to replace the pulls:

To replace the pull simply use a small pair of flat nose pliers to gently lift the slider hook at a slight angle, remove the damaged pull-ring, replace with the new one, and tamp the slider hook down to secure the new pull in place.

Kind regards,  Booq!  and us of course