Yuck ~ I am another avid Costco shopper and shop enough there that my membership is 'free' every year ... IME their Kirkland brand generally is better than some 'brand names' depending on the item.
Definitely GROSS to come across something like that .... however as gross as it is to think about ~ with anything manufactured that was 'fresh and flash frozen' there is this risk ~ these are fruits coming from NATURE and being rinsed in mass and flash frozen and bagged ... so since bugs 'live' off fresh fruits / veggies too there is the small risk of a bug getting through the clean and rinse system at the manufacturer ~ to be honest I myself have eaten FRESH from the garden food where one of the little buggers was missed when we washed the lettuce! I personally would be more grossed out to find something that is not 'natural' in my food like a bandaid or fingernail or what not
Plus not to freak you out further - but this is likely not the first time you've eaten a bug in your processed foodGoogle 'how many bugs are allowed in food supply' and you might NEVER eat a processed food item again! Amazes me what the Food inspection agencies in different countries 'allow' into our food ~ so in this case how many bugs and bug parts are considered SAFE in our food supply and sent out to consumers KNOWINGLY ... and not just in cases like this where you can SEE the product but in things like CHOCOLATE BARS where they bug is missed in the collection of coca beans and is than pureed into the item .... and all the other things cooked, canned, frozen and so forth.
Not to mention that 'bugs' are a common additive to create food coloring and flavor enhancers in our food supply. Did anyone see the big news story on the Starbucks which was outed for using 'beetles' in their red flavored drinks and not disclosing this to their 'vegan' customers that they were eating an 'animal bi-product' or the Jamie Oliver revelation that vanilla flavoring in many processed foods comes from 'beaver anal glands' because it is 'cheap' and apparently tastes good?
Yup the more I learn about 'modern food processing' the more I want to go back to Little House on the Prairie times where we might not have had as much choice or convenience but we knew exactly what was in our foods!