Corrosion is not immediate, so it working after the spill doesn't mean too much. Also, depending on what was spilled, it may just be gummed up(if soda or something sticky like that) and preventing contact. I don't know what type of switch/contact is in there, if it is a microswitch, you might not be able to do much. But taking it apart and a good dose of contact cleaner could do the trick, if that's what it turns out to be.
I am under the impression that you are not able to use the switch to lower from off-road to standard, correct?