You will certainly know if you have them. One infestation in a sealed container seems able to spread amazingly.
VHJ I agree with you about the cockraoches. I hate them. When we lived in Broome the first thing we did every weekend back was fumigate the entire house and leave. I used to keep absolutely everything in the fridge. eg coffee, tea. Our cutlery was in a sealed container and I re washed every plate before I used it again.. For about 2 years after we left I kept thinking I could see enormous cockroaches running on the floor.