if your tongue is swallen as if youve been biting it yet you know you havent been then you may have had a seizure, as tongue-biting often occurs during seizures. The strange thing with seizures is that you dont even realise youve had them because your brain literally switches off in a way, so although you have a seizure you never remember it because its almost like you weren't there. 1 in 20 people will experience a seizure at some stage in their life, but things like stimulants, excess alcohol, lack of sleep, etc etc all lower your seizure threshhold. If you think you may have had a seizure it is very important you go see your doctor, you may be advised to then go to hospital for CT and MRI scans to check for lesions.
This is a very important thing for drug users to be aware of ... our brain does have limits.