You are off the hook, for now:
1.) It appears in this case that the case was removed from the docket by the court for want of (lack of) prosecution.
2.) The Rules may well allow for a case to be reinstated IF the plaintiff moves to reopen the case. (Check them.)
3.) Considering the usual way that collection lawsuits seem to work, the fact you were willing to fight all the way to trial made an impression on them and they decided to "bail out" before they spent more on the attorney to try to collect than the debt was worth! And, yes, it's possible for a creditor/plaintiff to "bail out" by simply not doing a thing. This is a common way they do it; the fact the record says the case was "stricken" indicates that the case had already been assigned a trial date so a mere voluntary dismissal without prejudice (or one initiated by the court) would have been incorrect.