Sodium Spike Necessary once in awhile?

For the longest time I was at 168, then one day i took in a HUGE amount of sodium (Subway and the ever delicious Sushi are the culprits). Now i usually get 2400-2600 sodium a day, but this particular day i took in a whopping 6478! Well the next day I weighed myself, and like magic, i weighed 166! Strange, but was the sudden sodium spike the culprit?

i have no idea, i've experienced the same thing though. it's really weird..