I recommand you to write a ticket for the lost cat that you opened and who's inventory you copy to your inventory. That's what I did at least and I got replacement.
First thing you need to do is click in the top the PEDIGREE menu. It opens a list with your cats you own in SL. The opened box will mostlikely be listed as box there. You click on the listed box and it should open it's family tree. In the family tree of the box, you should see the stats of the boxed kitty and who's it's owner (you in this case) underneath there's a line starting with ID:
You copy the entire mix of numbers and letters that comes after the "ID:".
Once you have done that, switch in the top of this website to the SUPPORT menu. There you should see a couple of buttons, one says "SUBMIT A TICKET" touch it. Then you paste the ID number int he ID field, as subject you do something like "Broken box" and as message you file in what happened to your box and how it got broken. Then you get it replaced within 24 hours.
I hope this helps
Greets
Dario
Thank you so much Dario for your help. Any suggestions how to help the 2 kitties I do have sleep?