If you buy a crown from any shop, have a look at it. If it's really dried out you'll probably lose it. Also rhubarb doesn't do well in pots - it makes deep roots and a huge crown. If you want to grow it in a pot, then start it in a small one that will take the crown plus around 2 inches wider and deeper. If you put it straight into a huge pot and water generously you will simply drown it. When the crown in the small pot shows signs of life and roots appear through the drainage holes at the bottom of the pot, you can transplant it to a larger pot (gradually building up to the final size). Bear in mind you can't crop the first year as the leaves are needed to provide food to build up the rootstock for future years.