Short-term memory loss may be due to a multitude of factors that include smoking dope, but this is not the only cause. Other prescribed drugs may severely impair memory and these include most drugs in the Benzodiazepine class such as Valium(R) containing Diazepam.
Most cases (that may not be clearly attributed to underlying disease)seem to be transient in nature and recur erratically. Many causes have been attributed and minor ones such as hypoglycaemia (low blood sugar) because you've skipped breakfast may easily be remedied by a chocolate bar of other rapid sugar/carbohydrate source. Insufficient sleep is another common cause and one may resort to coffee as a temporary measure, although overdoing coffee will have the reverse effect after some time!
Remedies that claim to help Short-Term memory loss may be based on Ginseng root, and I know many people who swear by this type of remedy.
In Europe a drug by Servier Labs called Arcalion containing Sulbutiamine increases physical resistance to fatigue, neuromuscular efficiency and learning and memory and improves the metabolic functions of the cerebral cortex with resulting improvement in short-term memory. I'm not sure about the trade name in the US or even whether it is available there. Again I know people like my grandmother and a few friends who use it during exam times and who claim to improve mental performance following continous use.
I have tried several rememdies in the past, but I'm terribly sorry that I can't remember whether they were effective or not;)