How bad is road salt for my bike?
For a one-off ride in the salt like that, you should be fine for now if you lube the chain and wipe it down. Give the bike a good washing whenever the weather warms up enough to turn on the outside spigot.

In my experience of riding through road salt (and grit, which is probably just as bad) on a regular basis, the bike tends to need a new chain every spring, and a new cassette and bearing overhauls about every second year or so.