Yes, I agree jb. I would never support the entire weight of the trailer on the stabilizer jacks either. But I think it would work out using that with a tire jack.
I dont think you did anything wrong either, other than what l2l mentioned. Other than that, theres not much else to do wrong. It is good that they are going to replace the entire jack, since you just got it and wont cost you anything. That will, if nothing else, give you peace with it not happening again, whatever it was.
its hard to say without seeing whats going on, but depending on how high it currently is, if you had some tall jack stands I would try that. You could use the tire jack to jack it up, and slip some jack stands up under there near the jack itself on the frame.
And of course the other question is, does your jack extend high enough to jack it up off the ground, as it sits now?
So is your jack bolted on, or welded on? I assume its bolted, since your going to remove it??
Are you just going to try to remove it and then hook up to it and take it in? Then unless they have other equipment, they will have to work on it while its hooked to your truck. Or are they just going to give you another jack to take home and install yourself?