Someone mentioned you could sift it out. I recommend getting a fine-mesh kitchen or dirt sifter for the time being until you sort out what permanent soil bedding you'll be using (Spot clean and sift). Will help you at least be comfortable knowing you got the rocks, twigs, and synthetic materials out of the coconut fiber. I'm not sure if Zoo Med can be held liable for these small traces of things besides the coir. Since it's all factory produced and it's never certain that there's not anything else mixed in. It's definitely worth a shot calling them up though and trying to get it reported to the department to see if this issue can be fixed. Telling them your situation, etc...

I've also found small strips of white plastic mixed in with the coconut fiber. Took that out, but I've never found rocks like you have.

In my case, I buy the zoo-med coconut fiber bags already made in the bag (The bricks are annoying and the same amount of money) mixed with EarthGro topsoil found at Home Depot and a few other hardware or plant nursery retail stores. 50/50 mixture of both for the coconut fiber to hold humidity, topsoil to fight bacteria and fungal growth, and provides a looser consistency. The only problem with the EarthGro topsoil I bought, it has traces of mulch in it. I've been picking out pieces of mulch and I found a stink bug or some other type of beetle in the soil that I threw out.

I don't stress about some of the mulch left in there though because I feed my frog in a separate feeding bin. Still like to pick out what I can find though and throw it away. Doubt there's any plain topsoil that is just straight dirt without mulch unless you go into your backyard provided that there's no pesticides or fertilizers present.

Hope you get everything worked out for Grif and Loki. Gotta' keep them healthy .