As all has stated, yes it does absorb just as other mucous membranes will. The problem with the throat is that it will be taken down to the stomach by saliva and loose mucous. The further down, the more quickly it will move into the stomach.
Any which makes it to the stomach will then be subject to hydrolozation and secondary metabolism in the liver which will render it about 30% available out of whatever makes it into the stomach.
A note of caution and the throat.
SWIY should remember that cocaine
is a powerful local anesthetic and causing numbness in the throat can be dangerous if SWIY is eating food. Poorly chewed food or sharp objects like potato chips could cause small tears in the esophagus and can be quite painful once the anesthetic effects have worn off and SWIY tries eating again later.
So, SWIY might not feel it, but there could be damage being done by eating food with a numb throat. Just remember grandma's advice to always chew your food plenty of times before swallowing. Nacho cheese Doritios have sharp edges, you know...