Hi,
its a normal practice by custom official to randomly open and check whether the ingredient is actually the same as mentioned in document, atleast that's the practice in region where i work. That container is definitely used since they do not open 100% packages rather randomly select some to open the package, once they are done with they do close the package (various ways) and reseal the container with their own seal, this seal is traceable with the document they provide for release of material.
So the material can be used, as long as seal traceability can be ensured, and if the particular pack which was opened is not usable condition then definitely its a loss.
I have seen some practice of attaching a sealed small sample bag with same ingredient & with details along with the ingredient packages visible while opening of container so that custom most of times they take sample bag for analysis rather than opening the ingredient packs;