If they can give you a claim number then you can verify their story with the court. If they cant, or don’t want to, it’s unlikely that they ever did sue you. If they had a judgment they would have already been garnishing your income. They usually don’t threaten to garn if they already have their judgment they just do it and wait for you to call them.
Read more here on how full of hot air collectors can be: Bill Collector Lies
Either way, it doesn't sound like they are garnishing your pay so if they do or they don’t have a judgment why cry over spilt milk until you find out?

