It happens a lot, and it’s confusing. The easiest way to figure out how to tell if someone blocked you on snapchat is to search their exact username. If the profile doesn't appear, but you can see it in a friend's profile, you may have been blocked by that friend. Look at your chat history too because with a blocked chat, you'll find that it gets deleted or stops sending. Don't assume anything, since they may have deleted their account as well. I located a step-by-step guide on the Boostbysocial blog that outlines all of the indications.