Heres some info i found that might help some people clicking on this thread for insight.

Oral Fluids
Saliva, an oral fluid, makes THC, the active ingredient in marijuana, difficult to identify. Only a tiny amount of THC is present in saliva during marijuana use. So, unless saliva is tested one to 14 hours after THC is inhaled or consumed, it is unlikely the drug will be detectable. It is also possible that a saliva test will not show THC was used at all, depending on the amount of the drug taken into the system.

Test and Accuracy
The saliva test is administered by swabbing the inside of the mouth, and the bottom teeth and gums for a minute or two, until enough saliva is collected for testing. It is the least accurate way to determine whether a person has been using marijuana, due to the inaccuracy of the test after a day post-use.

How Long Does Marijuana Stay in Saliva Tests? | eHow.com