If it snapped you are ok. If you leave it tuned too high and it sits there for a long time, you may have neck problems. I wouldn't worry too much about it.
Nothing too permanent could happen unless its a really old bass. Most likely if you have the bass sitting around for too long missing a string you'll need to to re-adjust the truss rod. Its basically caused by uneven force exerted on the neck, having all of the strings on balances this out.
