If a button comes off (and I have never seen one do that) it is fairly simple to replace. Return to the Dr's office, and using one of the aligners as a template, the button can be redone.
What Happens if a Button Falls off from my Invisalign?
Doctor Answers 2
We can replace lost Invisalign buttons
What to do when Invisalign button falls off
Your Invisalign dentist will be able to replace the attachment. Continue wearing your trays as normal and make an appointment. Your dentist will be able to use the tray you are wearing to make a new button. Not an emergency.