If someone has unfriended you, blocked you, or deleted you on Snapchat then just try searching for their username on the app, and if you don't get any results, then it means they've blocked you.
There's actually a pretty good explanation of things to look out for to let you know as soon as possible that you've been blocked on Snapchat.
If you really suspect that your friend has blocked you, then you should probably check it out: //technology.blurtit.com/3989144/how-do-i-know-if-someone-blocked-me-on-snapchat
