In my opinion, every persons body works differently. If you haven't taken meds in a few day's, feel symptoms, then it's quite possible lack of hormone or Vitamin D is causing, only sure fire to know is labs or personal experience. You can contact your physicians office, have them fill a script for ya, pick up at local pharmacy. Good luck.
Since Synthroid is a longer acting medication, it would seem that not having it for only 3 days wouldn't produce severe symptoms, yet, but as AJ said, we're all different, so it's very possible that what you're feeling is due to not having your Synthroid.
It sounds like your levels might have been borderline to begin with, so missing 3 days of med, really did a number on you, in a big hurry.
If your meeting is just about over and you'll be home soon, you're probably just as well off to power on through and get back on med as soon as you get home; however, if you have to be away yet for several more days, by all means, move mountains to get some med or you're going to be very sick, possibly to the point of having to go to the hospital.
For future reference, whenever you pack to go somewhere, whether it be vacation or business, meds and vitamin/minerals should always be the first thing into your carry on bag/suitcase. As I take each one of my meds the day I'm leaving, I put them straight into a zip lock bag and once I've taken them all, the bag goes into my carry on bag/suitcase, so it never leaves my sight...
I strongly recommend that when you get back on med, and get stabilized you have your levels (not just TSH, but Free T3 and Free T4, as well) retested and make sure they're well up in the ranges, as recommended.
"If your meeting is just about over and you'll be home soon" - I meant to add "today or tomorrow" - don't wait any longer.