Unrefined Materials Disappeared After Taking Them Out Of The Bank

So I took out about 199 materials from the bank, checked my inventory afterward and they were all gone. I checked the bank and they weren't there either. I know I can't do anything about getting them back, but is there any way to prevent this from happening again?

 

You probably reached the maximum amount of unrefined materials you can hold in your inventory, which caused them to drop onto the ground, and you probably didnt notice that and it despawned.
As for how to prevent this, be more careful about how much you can hold and how much you are taking out of the bank.