Should the crown that fell off be kept in liquid until it's put back on?

I'm sorry to hear that your crown came off. The crown does not need to be kept in liquid until it can be put back on. It's important to see your dentist right away for an evaluation. If the adhesive failed, the crown can be recemented. I hope this helps. Click save on the save button below my name, so that you may ask me more questions in the future.

Hi:You do not have to store porcelain or metal crown in liquid.  However, you should get it recemented right away before your tooth moves.Best,Dr. Maddahi

The crown does not have to be placed in water, but secure it so that it is not inadvertently lost. Should a crown come off, the most important thing to do is see your dentist as soon as possible. Shifting of the teeth often occurs and may affect the fit of the crown, so don't delay. Good luck!