Nothing against you, but I've always been a firm believer in having a backup bass tuned and ready to go in case of mishap. Any time I've worked with Pro's, this is the norm, and it kept its tradition once I went part time. Many will scoff here and say, "I've never had an issue, no reason to bring a spare." My answer is, "that will change after it happens once or twice and it shuts down the show." You got lucky and was able to get through just missing a string, but a 10 second bass change would have been easier. Not pointed at you again, but usually after a mishap, what I say makes sense.
I carry an extra amp, often two cabs, and anything else (cords) that might stop a show. Anything mechanical can break, and will often pick the worse time to do so.
I'm sorry you had the mishap, but I'm glad to see you learned from it.
Me? I broke one string, a G string after repeated boils, practicing in my room when I was 16. I've had just about everything else break on a bass, but only that one string.