It is certainly possible that she pulled something, but if it had occurred during the trip, you are correct that symptoms should have showed up after a night in a stall. However, horses are capable of many odd things that don't make sense and I completely understand your hatred of waiting. Mine was just in the hospital for 3 days for a bone scan, radiographs, and back injections and I think I burned out a retina staring at my cell phone.
If the stifle is hot, ice and cold hose are never a bad idea. If you have some bute, that will help with inflammation as well, but don't bute the night before or the day the vet comes so they can see the real deal. That's about all you can do until the vet shows up. Then the answer is probably time -- I am learning this is most often the case, you'd think after so many years around horses I would know this by now, sigh.
Solaris -- 16 hh Appendix Quarter Horse = MY DREAM COME TRUE!We Are Flying Solo