Snapchat has so many peculiarities that even experienced users can find it challenging to keep up with all its oddities; one such quirk is when users unfriend others without necessarily notifying you; Snapchat does not notify anyone when your friendship status changes, which can be particularly confusing for newcomers.
Communication on Snapchat typically begins with photos and videos (called "snaps"). To create one, tap on the big camera circle then use various editing tools and filters to personalize it before sharing or adding to your story - an archive of 24 hours worth of your day that anyone can view for public consumption. Snapchat also features messaging services with texting, calling and callback features for added functionality.
Even after someone unfriends you on Snapchat, they won't have access to your private stories and posts. If they need to contact you directly again, they must send a message directly to your Friends list instead of being added back as friends on Snapchat.
However, if you want to confirm that your ex removed you from their friend list as opposed to simply blocking you, Snapchat makes this easy by allowing users to search by username. If their name doesn't show up in search results it means either they have deleted their account or unfriended you.