Pretty much this.
If you did some warm-up work and one or two "work" sets (a fraction of your entire intended workout), I certainly wouldn't consider that a legit workout.
Very much this.
It depends on exactly what you did in there. If you only did one work set, but it was a near-max grinder with two rest-pause reps, that's different than if you just did a straight set of 12 not to failure.
Also, look at it as a lesson in better time management. If you step into the gym and see it's crazy crowded, realize ahead of time that that you might not be able to stick to your game plan as-is, so you'll have to make adjustments. Depending on exactly how much time you did have available, and your training goals, you could've made a session work instead of stressing over this non-issue.
I'm curious... since you started this thread yesterday and were considering training today, what did you end up doing?