Is it rape if you were too high to remember anything that happened, until you find out the next day you had sex with a stranger?
Depends on the local jurisdiction.
Some jurisdictions view it as rape if you are incapable of giving assent, for whatever reason.
The very nature of you being there high to be expected it would lead to it? Crying over spilt milk or trying to hold somebody responsible? Is irresponsibility, rectify that situation. Why get into such situation in the first place? Anger and guilt will eat you for the rest of your life.