I was thinking the same thing as I have A LOT of water retention right now as well and it has been 2 weeks - but I have been eating more carbs to stave off the alcohol so that is part of the issue.
I have struggled with this water retention off and on the whole time I have been drinking. Years ago I gained 15 lbs virtually overnight - it eventually went away. The doctor told me to drink lots and lots of water.
If they did blood work at all in the ER, they would have found something if it was concerning.