Sometimes using SOAP with the Magento V2 API you may search for a product's image (by calling catalog_product_attribute_media.list with the sku as only argument) and receive this hilarious message:
"Product not exists." <-- you can't make this stuff up!
Hilarious but sad, because there's the image right there, laughing at you from the website, and yet your API doesn't have access.
luckily there's an easy fix. in short: append a space to the end of the sku. done. psha. magento, we love to hate you.